i did my darndest to find any iota of difference in sound quality between an ipod touch and a clip zip, then i bought a cypher labs algorhythm solo and did my darndest to hear a difference between that rig and my clip zip. same when comparing my home computer rig via an objective dac and objective amp via foobar and wasapi.
i finally came to the conclusion that there was none, and if there was, the difference was so minute that i would never ever know the difference anyway.
maybe some players out there are skewed in their sound reproduction, and oddly you mostly hear that about there really expensive ones, but otherwise, creating a player that just plays correct, flat response, is not really that hard.
The only player left in my rig that i actually use is my clip zip. simply because its the most convenient, and it sounds incredible with the right headpones and right eq settings via rockbox.