Will a high quality preamp really make a difference in sound?? Also speaker cable

Every system is a different, but a preamp makes a difference in my system, and so do the cables.

Using junk cabling is a sure way to prevent your system from being optimized, and evolving into something special. With the options available today, there’s no reason to risk the cables being the bottle neck of potentially good system. There are lots of good reasonably priced and DIY cables. Mogami, Blue Jeans, Carol, Belden, SKW, Monoprice, Audioquest, GearIt, and others. No need to spend a fortune, but good cables should be quite audible.

Yes and Yes.  

Yes to both

I think the preamp is the most important component in the chain.   I usually spend over budget when I replace a pre so as not to make a lateral move.  

Unless you've had a world class preamp swapped into an already good system. It's hard to explain how pronounced of a difference it CAN be.  May take trying a few but a great one can really elevate your system to a different level. 

What improvements are you looking for, what equipment and cables/interconnects are in your system now, what’s your budget, and are you looking for new or used?

You can’t fix a crappy amp with a better pre-amp the same way you can’t fix a crappy pre-amp with a better amp. Every component plays a role formulating the end result. The key is to get a clean sound signal from start to finish. Quality cables transfer the signal between interfaces without introducing noise or loss. The bottom line is crappy in, crappy out.

I agree with @oddiofyl that a good preamp is of paramount importance and a hard thing to get right. Simple tube circuits are the best solution I've found personally.

My amp has a non-working left channel...sent it back to the factory to have a look see and fix.   I looked around the room and noticed the expensive power cord for the amp was lying on the floor not doing anything.  Stupid 82 old me replaced the "upgraded" cord on the CD player with the expensive one that used to drive the amp and was bewitched by the improvement.....just ordered new power cables for the rest of the system. 

The preamp is nearly as critical to the sound of your system as the speakers.

Common audiophile wisdom - active preamplifier is extremely important.

Speaker cables, like everything else, are important too. My speaker cables cost new or used as much as my speakers. Perhaps I overdid it a little but I haven't had to replace them in 25 years, and my system now sounds incomparably better than 25 years ago with the same speakers and cables. But it's a modest system, both speakers and speaker cables cost $1500 new 25 years ago.

Back in 1992 I purchased a AR SP-9. It made a huuge difference! It opened up the soundstage width, depth and detail. All improved immensely! It was though I walked into the room of the performance.

Put world class preamp in any decent system and you will probably agree with me. It is a transformative experience.   Makes the whole system sound better and live up to its full potential 

There are many great speakers out there hobbled by a mediocre preamp.  Or a so so amp.    Lots....  Part of the reason we've all been chasing better sound.  

 I think spending as much or more on amplification than speakers yields great results.  

More on amplification, definitely more. Unless the very top level where it might get equal, I don't know. Give any good speakers a signal and they will sing.

Right now I'm using 2 identical Anthem power amps MCA 225, NAD C379 preamp, Cambridge audio cxn100, and a Marantz single cd player as a transport using the dac inside the NAD. As far as speaker cable I'm using some that I found on Amazon and it seems to get the job done, the name of this speaker cable is WBC.

One of the most  significant jumps forward in sound quality in my system occurred  when I made a substantial upgrade in the preamp. The only thing that made as much difference was room treatments. Like most of this stuff, it’s probably system dependent, and others may have had a different experience

I went from a Rogue Audio RP-1 to an RP-7–almost triple the price, and it made a marked improvement.  As for speaker cables, I was a bit of a skeptic, figuring that “decent” cables in the $100 to $300 range should be enough.  However, I purchased a set of Silversmith Fidelium speaker cables and was astounded by the improvement in sound quality.  My non-audiophile wife even commented on the “major improvement.”  So, quality cables do make a difference.  In both cases, however, keep in mind the law of diminishing returns. Will a $50,000 set of “Cattywumpus Delight Mastercables” be 50 times better than the Fidelium?  Not likely at all.  Ten times?  Not likely, as well.  Figure out what you are willing to spend, and then do some research and try out a few ifdealers will permit a test—I the the Cable Company has a trial library.  Specific cables may sound different in different systems.  Others may disagree, but my experience says cables do make some difference.

You know, some seemingly small changes can make a big difference...I believe we should first work from the source outward.  For example, get the speaker cables off the carpet!  Can make a big difference, a whole upgrade!  Then get revealing interconnects, to me musical, revealing but not harsh ... Speaker cables...buy used! Same for Interconnects... can get excellent  values for outstanding sonics..  Then, I'd focus on the speakers as they have the ability to assign the sound, music characteristics you most appreciate...certainly, there are certain synergies between some speakers and electronics...but I've found that if you get the speakers right and the foundational basics "right" you may be surprised how good your current pieces work...or at the least you know what the new candidate brings to the equation.  IMHO, we too often forsake musicality for a "different" sound.  To me, music is an art, not so much a science...I'm a romantic!

My local hifi store brought up a good point; they said that the only thing between your amp and your speakers are the cable.

Absolutely, but talk is cheap. Don’t believe anything or anybody, just listen yourself and make your own decisions. Has the dealer not done a demonstration for you, comparing what improvements can be had by moving up the speaker cable ladder? Same goes for pre-amps. It is always nice to know what is possible, even if you can’t afford it today.

I think the question you should be asking is what is the weakest link in your system. I don’t know what your NAD pre- section/DAC or WBC speaker cables sound like, but maybe you should be upgrading the DAC first? And even before that: Are you using the manufacturer’s interconnects that came with the equipment? That would be the first place to upgrade- the best speaker cables or preamp in the world won’t make up or re-generate the details lost by poor interconnects or an inferior source upstream.

I’ve owned Rega, Naim, Linn, Macintosh, Denafrips preamps, and currently a Supratek tubed preamp. None of then sound alike. All vastly different. So yeah it matters. Another thing to consider with speaker cables is trying both copper and silver. That’s probably the biggest difference I found in different types of speaker cables. Be careful with silver tho, low quality silver cables may lead you to falsely believe they are too bright... they shouldn’t sound bright at all. I’ve found the copper will give you a heavier presence in the mids and upper lows, bit darker, warmer overall, also recessed or laid back highs (in comparison) to silver which will reveal more details more open airy soundstage from top to bottom. One is not better than the other, just different characteristics. Ether way you go you will gain and lose something, so in the end itll come down to personal preference like most things in aduio as it should. Best of luck hope this helps

@mcmike +1. Silversmith Audio Fidelium made a big improvement in my system. I was surprised. I didn't actually expect much from a speaker wire. 

These speaker cables would be a big improvement over your Amazon cables for not all that much $$$, and if for some reason they don’t work out you could sell them for little/no loss. 

https://www.usaudiomart.com/details/650192681-acoustic-zen-satori-speaker-cables-25m/

And as others have mentioned the preamp is huge and should be your next upgrade along with a good separate DAC.  What speakers are you using?

Several years ago, @soix gave me the same recommendation for the Satori cables. I had tried 4-5 others methodically before buying a pair of the AZ cables. Putting these in my system made me a believer, they will improve your system.

Same goes for a good preamp. I was using an NAD preamp and made a low cost upgrade to a Schiit Freya+, a very significant improvement. I have gone further up the chain since then, with more improvements. So yes, a good preamp will make a difference. And then some good interconnects…