Thanks for the suggestions, everyone. I'm still slowly working through my perspective on this, going back to old favorites while also checking out stuff I hadn't heard before. Seems like it will take a bit of dwelling on this topic before I can come to any conclusions I feel comfortable with.
I feel kind of silly asking this, but how do you all choose to listen to the music (outside of the actual games)? I've been using headphones, but I've been wondering if some of the simple stereo speakers I have lying around would give a better representation of the audio.
Players/plugins is something I'm curious about as well. As far as I can tell, the latest NEZplug++ (found here) is the best in terms of everything but play-around features, and Winamp is the preferred player to use it with if you want the benefit of proper m3u handling (although I may simply have KbMediaPlayer set up wrong).
As you may have noticed, I'm kind of paranoid about the possibility of having a suboptimal listening experience...