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

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!