Help wanted: Bass!

inna,

Yes, but subs can be a nightmare if you have no control over their placement, room acoustics or EQ. In this case it's the perfect storm for @rbshauman

I'd get zero.

Given the ability to control at least 2 of the three pre-requisites, I'd start with 1 and see what's missing. The value of a second sub may be smaller than it's worth.

I believe that Emerald Physics is distributed by Wally Underwood at Underwood HiFi.  He also handles the DSpeaker products which include a competing (and IIRC somewhat more expensive) bass eq device.  You might call Wally to discuss the relative merits of each.

Greetings RB,

I have CJ PR12s and an LS 16-2 as well with B&W Signature 30s, Gyro SE SME Benz Ebony CJ PR15, AYRE DSD QB-9 Mac Mini with AQ Diamond USB cable. Since we have very similar systems I thought my experience might be helpful. I too always wanted a little more bass than I had. Initially I had Transparent Ultra speaker cables. MM2s provided more detail on top but nothing in the mid and bottom end. They went back. I got Cardas Golden Ref ICs and biwire speaker cables throughout. This was an all around improvement. They stayed. For years. 
Still thought things could improve so I tried REF Level biwire Anti Cables for speakers. Unbelievable difference in flow, EVERYTHING improved but most significant was the improvement in the bottom end...deeper and freer with no negative effects on the top or mids.
They stayed and are still in use.

As to tube rolling...Currently have KT-120s from Kevin Deal at Upscale in use. Huge improvement in bass weight and dynamics. Immediately apparent and easily discernible.
But not as lush and wonderful sounding in the mids as NOS Tungsols which create the kind of sound I imagine we are looking for when we buy tubes in the first place. These are the tubiest
of the power tubes I've tried. Russian SED C KT 88s were somewhere in the middle and had a good overall balance...more punch than the Tungsols, but not as lush. FYI the driver tubes are NOS RCA 5751s at V1 on the 12s. So IMO if you really want more bass, the new  KT120s will not disappoint. But in adding bass, you will be markedly changing the character of the 12s.

Which brings me to the 6922s in the 16-2. Stock CJ tubes very nice mid range type of tube,
not overly warm and not bright. NOS Tungsrams are really warm and full and lush sounding.
NOS Siemens Rohrs (blue box) are champs at adding tremendous air and a great soundstage. The beauty of the CJs is that you can tune the system to your tastes, but I have yet to find the best of all worlds at any one time.

The Cardas GRs ICs are a good middle of the road approach and my preference is to get the mids sounding as full as I can. The best anti cables ICs are also very good and sound very smooth but yet detailed. With the KT 120s I preferred the warmer balance with the Cardas GRs which I didn't like as much with the Tungsols or KT88s. For those tubes I use the AntiCable ICs. For me, it's all about tuning the system to suit your taste, which changes, for me, from month to month or year to year.

My room is much smaller than yours, so I have no issues with the bass since I added the AntiCable speaker wires. UltraFidelis run by Jonathon Spelt has a great article on subs at his
website ultrafi.com. He's a Vandersteen dealer and makes a cogent argument for that design philosophy and implementation which makes sense to me in terms of integrating with our systems. But I have no first hand experience with it. I suspect his would be the best approach
but also costs significantly more than you are talking about.

 I do have experience with REL subs (T9 newer) and can say they are capable of adding weight and energizing a large basement room or a large living room (T7older) with KEF LS50s
But these are in systems significantly less sophisticated than yours where integration was not as critical. No shortage of theories and opinions to be debated regarding subs. All I can say is the RELs worked for me in other systems and were a simple, relatively low dollar solution for adding more bass and I thought they represented good value. I was never listening thinking 'boy these don't sound integrated and are disjointed,' I was thinking "man this sounds really good." Buy them used here and you won't get hurt too badly if you decide they are not your cup of tea.

FYI, I have an Audio Research REF5 SE on the rack now. The LS16-2 goes just as deep and is fuller harmonically in the lows and mids. The AR is a  tighter down low but doesn't go deeper. The AR is definitely faster, cleaner, more detailed and more dynamic,  due to the Teflon Caps I'm guessing, but I'm not sure I'd rather listen to it over the 16-2 over the long haul.

So Anti cables, KT120s, Sub should leave you dazed and confused for months to come!

Enjoy the music!
RBP

..buy a subwoofer...the cheapest and easiest way to fix your issues..

Since this has not been mentioned:

The first thing to check is the phase!!

Try swapping the red for black connections on the back of the speaker (one channel only), put on a record with some bass impact and see if the bass is better or worse. If the speaker is out of phase bass will be poor and with some speakers and some rooms you may not notice that the imaging isn’t what its supposed to be. So it might be that the imaging will improve as well if phase is a problem.

Another thing that can cause loss of bass is the length of the speaker cables. One advantage to running monoblocks is the ability to place the amps close to the speaker to allow you to minimize the length of the speaker cable. This usually has a bigger effect with tube amps than solid state due to the output impedance of the tube amps being higher. This is exacerbated if the bass region of the speaker is 4 ohms instead of 8 or 16!! Generally speaking a meter and a half is the upper limit with nearly all tube amps unless you have 16 ohm speakers and you don’t. If your speakers are 4 ohms the limit is more like one meter and the cables had better be pretty heavy.

Its also important to make sure the connections on the amps and speakers are as tight as possible. DO NOT OVERTIGHTEN or you might really regret it.

You may also be experiencing a standing wave in the room; often a problem when the room has regular dimensions. If this is the case no amount of EQ will fix it. I advise staying away from EQ as you will find that the EQ exacts a price which is a loss of transparency and musicality. Its better to find a solution by other means. A standing wave can often be cured by moving the speaker somewhat. If you are stuck with the location, back the speaker up as much as you can and fiddle with toe-in.

Of the subwoofer suggestions, I second the Swarm made by Audiokinesis, should you find that subs are indicated.