I cant imagine there is too much of a difference, considering MP3s sound crappy to begin with, unless you are using lossless compression. What's the sonic difference between the headphone out and the amp? Is it possible to describe?

Could anyone actually find out what the headphone circuitry in the ipod is, and a writeup of specifications for it? I can soon, I have a Nano 1st gen opened, but I'm too lazy at the moment so I'll do it later.