Thanks!
always fun to test the ears.
I agree with a few of the commenters, FLAC or other lossless format is the way to go. This will allow you to convert to whatever future formats come along without the need to re-rip the discs.
I've played around a bit with other files here at home, and yes it does get tougher to ID things as the bitrate goes up, but not impossible.
Later,
todd