Okay, I gave it a listen. Granted, Ben Folds Five isn't my favorite, but I listened intently anyway.
Equipment: Used Grado SR-125 headphones plugged directly into a SB Audigy. I listened to all tracks with Winamp (2.76) and again with Windows Media Player XP.
CBR 128 MP3 - sucks the poo from the poo tree.
VBR ~128 MP3 - can't tell the difference from the WAV.
CBR 128 WMA8 - also can't tell the difference from the WAV.
Just to be sure I loaded up the WAV and all three compressed formats for one song into a playlist, hit the random button, and hit the back/forward track shortcut keys a lot without looking at the screen. I honestly could hear NO discernable difference between the VBR MP3, CBR WMA8, and WAV. I couldn't pick out which one was playing. The CBR MP3 sounded like...mud.
I guess we could hypothesize that you have a dog's hearing and your
Sennheisers are just worlds better than my Grados, but I just don't see how, even then, there's enough room in there for a MAJOR difference. Even if I assume you've got both much better headphones AND hearing, I can't believe the difference would be anything more than minor.