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

@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…

Skip a preamp. It's an expensive volume control and most likely yes, it will color t the sound. 

But a good DAC with a quality analog volume control and you're set.

Audio Analog, Meitner and Playback Designs make such DAC's. 

Different preamps will normally sound different to various extents. I’d expect a “quality” pre-amp to make a difference if replacing one of low quality for sure.

I once replaced a Carver preamp with an Audio Research pre-amp.  Night and day!