CD Player Distortion?

I have a nice, musical budget system, and have made some recent "improvements" that have resulted in hearing a slight wavering of female vocals on SOME cd's with relatively spare accompaniment...I changed my interconnect from my CD player (Marantz SA 8004), to my integrated amp (Acurus DIA100).  The new IC is a Omega Micro Excalibur ribbon IC...the change was significant...much more information, yet remained very musical.  Next, I raised my speaker cables off of the carpet...WOW!...again, another gain in information presented...but, now I am aware of some slight but noticeable wavering of the female voice in CD recordings that involve minimal accompaniment...and loud brass can sound shrill...however, 90% of my CD's sound amazing...my ProAc Response 2.5's sing & boogie!  So, what is with the wavering vocals?  I am now getting a lot more information transferred, yet for the most part remains very musical and true to the source.  Most of the CD's I've had for years, but never noticed the distortion.  I wonder if this is simply a question of my system now revealing flaws in the CD or something else?  Any advice will be appreciated.