Further on the quality thing
Yes, listening to 128kbps MP3s is going to sound rubbish compared to archive quality MP3 encodings, or better still FLAC.
To say these don't improve the sound is rubbish though, even with the poorer quality encodes. Compared to shitty earbuds you get with MP3 players, noise isolating earbuds will reveal a lot more detail, depth and bass. It's the way they seal up the ear and create a good aucoustic environment in your ear.
Fact is that even crap encodings are made worse with poor earbuds. However they will also reveal just how crap encoding is. It was decent earbuds that got me to rip all my CDs to FLAC and use archive quality encodings for MP3, because of all the artefacts I could suddenly hear. It also stopped me downloading or borrowing dodgy rips off other people and I buy CDs now to rip myself (wouldn't buy downloads either).
Treated to decent quality source though these things shine. In fact the argument goes the other way. Don't bother with high quality encodings if you use the cheap ear buds supplied with the gadget.
Oh, and to go a step further, look into Crossfeeding. That's where you can get a more accurate stereo sound from headphones (problem being that headphones isolate the channels to each ear creating an "in head" sound, and are not like speakers where the sound from both speakers actually hits both ears). This can also make listening to stereo music less tiring. Some MP3 players have this built in now, and can be found as plugins for many media players on computers. Rockbox (the open source alternative player for many MP3 players, inc iPod and iRiver) also supports it.
Anyway, don't knock 'em till you've tried 'em.