Sound quality: frankly, who cares?
These days most things sound, well, good enough. And I think we’ve all done the deal that allows us to have all our music with us wherever and whenever we want it, in exchange for shall we say less than optimal reproduction (not that I can ever notice, to be honest).
However, I have been completely blown away by Octiv’s Volume Logic plug in for iTunes (initially found on the pages of Word). Basically it remasters your audio live, and the difference is remarkable. You should really try it for yourself.
The tragedy is that you can’t put it into your iPod, you might want to suggest that Apple allow them to do this…