Note that of course it depends on the .mp3 quality. Make sure it's 160 Kbps or above.
Now, I have the new 10 gig, and the earphones are alright....but nothing special. The bass isn't good at all...you lose a lot of the lower frequencies in many songs (I listen mostly to rock, BTW). A lot of it has to do with the fact that they're so small, which of course makes it hard to put really extensive hardware in them. I'm not that knowledgeable about speaker brands, but I have some Sony headphones that run behind my neck, and they have a much higher-quality sound.
greg