Weak link

It would be really helpful if you created a virtual system and put some photos from different perspectives and of the components. This gives us a lot more to work on. Just a list of components is much less informative. Sometimes, some simple things can have profound effects.

Just off the top of my head. Your system looks pretty well balanced. What is your power conditioner, do you have direct lines? These two would be the first thing I would look at. 

If room treatment of some sort is possible, I'd start there. 

weak link 1 = lack of subwoofers

Get a Elac Varro DS1000 and use the built-in calibration tool it comes with (very handy tool for all subwoofer noobs). 

weak link 2 = lack of power conditioner

Get a Niagara 3000 or 5000

+1 @knotscott I would spend some effort treating the room.  You have very nice components.  Room treatment is likely the best bang for the buck.  A pair of subs would be interesting as well.

To refrain others, without a budget, photographs, and a room description/dimensions it’s hard to make recommendation on your solid system.  I would address the following, in the order listed, for both will have a positive effect on SQ:

1:  Power quality.  A good conditioner like a Shunyata Denali or Everest, or an Audience Adept Response T series.  Then, if your home design permits without much construction cost, dedicated 20 amp power lines.  If possible, one for digital and one for amplification.  
2:  Room Treatment. 

That’s a great system. +1 for dedicated lines. If you are technically inclined get a usb mic and fiddle with REW to see how your room rates. Then look at room treatment. I have tried and like the WireWorld Eclipse interconnects, but you might try some other ones. I found them a touch on the dark side. I have not tried the ww speaker cables, but worth some research if you are on the lower end of their lines. 

Your room is the most important component of your system. If it’s not treated, you will be fighting to get th best out of your other components.

You didn’t say what you didn’t like about the sound you are getting. If you don’t like the bass, room treatments will help. If your don’t like the soundstage/imaging, room treatments will help.

I would hold off on buying any subs until you treat your room. Your speakers are sized appropriately to your room size so you might not need subs. My new house has abut the same size room as yours, and when I bought new speakers sized for my room, I pulled 1/2 of my room treatments out of my room that were used because the other speakers were too big for the room. I have subs but I don’t need them with the new speakers. I still use corner tube traps and 1st reflection panels.

1st, document what you are actually receiving at your ears, seated position

cd with test tones

Here’s one on eBay

Amazing Bytes CD with 29 1/3 octave Test Tones

Sound Pressure Meter, with bottom threaded hole for tripod mount

Meter on tripod, at seated ear height, at listening position.

Meter doesn’t need to be that precisely calibrated, you will get more or less answers relative to adjacent frequencies.

Make enlarged copies of the insert with test tone list so you can write down the results

Go forth informed

IF you have any tone controls, you can measure the results, and you can make adjustments for your personal taste, perhaps you have age related diminished hearing of high frequencies.

also, great tools to accurately measure the effect of alternate placement/toe-in.

room treatments are always good, but i agree with the get-a-sub--your kefs are great but i believe only go down to 35 or so.

Sorry I  didn't list it, but I have a single REL S510 subwoofer.

Room treatments.  Hands down this will be the best bang for the buck.  Why spend money on better/more equipment when it will be conflicting with sub-optimal room acoustics????  Good luck and cheers 

If this list of equiptment doesn't sound fantastic then there's something wrong with either the room or the placement/location/toe in/ triangle size of the speakers and proximity to the listening position. You really don't need any more or better electronic gear. IMO.

Is this a dedicated listening room or a family/living room?  Your options may be limited in a shared space.  I highly recommend ASC tube traps as the most versatile tool for shaping and tuning the space.  The downside is aesthetics for some.

Without spending money, I would revisit your setup.  Speaker position and toe in changes of a few fractions of an inch can make a big difference.  Seating distance is another thing to consider.  Inspect cable routing, keep speaker cables away from power cables.

You mentioned window treatments but didn’t state what type.  I like horizontal blinds and wooden shutters.  Varying the angle has a noticeable difference in the reverberant sound field.  
 

Count me as another that who will emphasize room treatment.

Adding room treatment to my current system, delayed other upgrades for a long time, since it improved my existing system.

is there a vaccine for upgradeitis?  I can't imagine your system not sounding fantastic but yeah I understand the disease "What am I missing???"  There is no cure but there is always ways to stave off the impulse to mortgage the kids and provide temporary relief. 

Cleaning all the contacts could be all it needs to get that last ounce of nirvana.

Moving your speakers is also great pastime (don't forget the blue tape to  return them back).  I'd also try moving your sub to different places in the room, closer to the wall or pulled out more into the room,  away / closer from the corner .   As you've become attuned to the way your system sounds that original setup might not be optimal anymore.

If you really need to spend money a couple of acoustic panels leaned up against the wall at reflection points would give you some ideas what treatments could do and if like what they do.

The last option if all else fails is for me would be to add an additional sub (or two)  to address the inevitable dead spots in the room.

It's the journey... remember it's not the destination but the journey

Deep333- I’ve used subs on and off for 30 years. Used rel subs on and off for over 20+ years. The most benefit I got is in a small room (12 x 11) and in very large rooms (27 x 16’).

And of course HT in a theater room. The best systems I’ve had didn’t use subs and the best audio setups that I have heard didn’t use subs either.

I agree that you can use subs to treat certain areas but I’d rather use a speaker that fits the room that gives me the bass quality hat I’m after without subs. I have subs just sitting there not doing anything and I’m fine with that

The only thing that needs upgrading if you want to go all the way is the Dac and streamer…I would get the Playback Designs MPD-8 and their streamer too…

I know it's been said over and over but I'll pile on for room treatments if possible.  Best bang for the buck IMO.  Just putting panels at the first reflection points is pretty much a game changer.  At least it was for me.  Very cost effective DIY panels or just hang some thick blankets to try it out.

Let us know.        

Room acoustic treatment and dedicated lines. I would re-evaluate after the room is done.

Get a BAACH 4 mac.  you will be amazed

+1 @jsalerno277 It amazes me how much better my gear sounded after investing in noise management.  The more I invest the more the gear keeps getting better!

I have a CAD GC1 and GC3 and 3 Akiko Corelli's in addition to dedicated lines and a Shunyata Denali.  I also have a PS Audio P10 that runs the digital stuff.  And I have taken all SMPS's off my dedicated lines.  I had SMPS's on the P10 and it absolutely shredded the sound quality from my DAC and Music Server.

After that upgrade you cables.  If you can't remember the names of your Wireworld cables it didn't hurt enough when you bought them.  I think really good cable prices are ridiculous but at the same time performance follows price.  The difference between $500, $1000 and $1500 cables is evident and discernable with noise management.

I believe a lot of the benefits of upgrading gear is missed without addressing the above.

+1 @rikkipuu I never explored the grounding devices that are on the market but it is all a logical progression from good cables and power conditioning, to dedicated lines, to improvements in grounding to realize a reduction in noise in the electrical signal that I personally find exhibits itself as grain and hash that once removed results as richer timbre and improved liquidity, silence in backgrounds, and space evident between images.  I should probably add ground improvements to my next system upgrade.  

+1 for Bacch4Mac, but Edgar (the inventor) will tell you that you absolutely need to treat the first reflection points.  Best of luck.

I would do in order:

(1) dedicated lines

(2) Audiophile receptacles (Furutech GTX-D (Gold or Rhodium to your taste), Oyaide R-1, or for the budget minded Acme Audio Labs cryo silver

(3) Acoustic treatment, GIK Acoustics is an affordable place to start with free advice

(4) Better interconnects and speaker cables

I am not surprised that you are happy with your system!

Your KEFs are brilliant speakers, in part because they try to emulate a point source of sound by having the tweeter and midrange concentric. This means they throw a very wide soundstage, are much less critical of positioning than ’conventional’ dynamic speakers, and do not exhibit the severe comb-filtering that others correct with room treatments. For those who are new to these speakers, KEF has a truly excellent 40-page white paper which explores their design decisions.

There are a couple of upgrade options for the speakers. The obvious one is to replace them with the latest meta incarnation. In principle, meta is a small plastic tuned absorber disk that sits at the back of the tweeter. A myriad other changes were needed to accommodate the meta disk. While meta technology is very successful in KEFs smaller speakers, I think the Reference Series is so good that the benefits from meta are marginal.

The other option I’d suggest will be counter intuitive to most people on this site. It is to consider moving to the smaller Reference 1 speakers. All the Reference Series use the same concentric tweeter / midrange. The difference is in the number of bass drivers (which are all identical as well!). The Reference 1 has a single bass driver, the Reference 3 has two in a d’Apolito array, and the Reference 5 has four. The more bass drivers, the more likelihood there is for comb filtering, where the time delay in the different signal paths causes cancellation and reinforcement.

I have used Quad electrostatic speakers for about four decades so I am used to accurate sound. I recently added a pair of Reference 1 speakers (not meta) and I prefer them. They produce a staggering amount of quality volume and credible detail.

Your DAC has separate paths for Direct Stream Digital so one upgrade might be to buy a Super Audio Compact Disk transport, which I would recommend if you play much classical music.

Are there many SACD recordings out there?

@crwindy 

Yes if you like classical and jazz.  Not so many for other genres.

Presto Classical in the UK has over 6,000 SACDs listed for about the same price as CDs. The also have a streaming service so you can see if you like the music.

Some rock is being re-released on SACD, such as Dire Straits.  Pink Floyd's Dark Side of the Moon in Dolby Atmos is awesome on Blu Ray audio.  Have a look at shop.2l.no for some real state-of-the-art recordings.

A system as good as yours deserves some DSD!