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

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…