I've got an iPod Classic (160 GB hard drive) loaded with ~ 25 GB of mostly 320 VBR MP3s. I don't have especially good hearing, but I've probably used it less than 20 hours because it was so painful to listen to any song with heavy cymbals, or words with "ch" or "sh" or similar consonant strings, etc. The treble was just hugely overbearing, either using some Sennheiser earbuds or feeding it into a stereo.

The last time I used it in the car, I had to turn the treble on the receiver down to almost nothing to make it pain-free, but then the rest of the song was very muddled, of course.

I was thinking about the chore of having to re-burn the MP3s with some low-pass filters or something, but found a post talking about the EQ settings available in the iPod Settings. Zooks! What's this! "Treble Reducer"!!11 Ahhh. :-)

It'll still need to be tweaked in the car, but it is so much better using that EQ setting. I wish I'd spent the time to look through the various settings years ago. :-/

Cheers,
Scott.