OP, just finished reading all the above posts and you've gotten lots of good responses. One thing I remember reading about was a similar situation as yours, harsh vocals/good instruments on a particular recording. Turns out, the singers mic had been wired in reverse polarity, everything else in normal polarity. And because you have some of the most resolving speakers around (I own Vandies, but I do know how good Maggies sound), I believe that the resolution of your system is bringing up the good, the bad, and the ugly from your music collection. My experience is similar. In fact, I mentally grade each of my albums into classes A, B, C, D, and F based purely on sound quality.
Tom
Tom