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

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.