difference between ipod models in sound quality ?

Believe it or not but iPods are the future of a desctop digital components.
In pro audio it's widely being used with great success.

I have a 3rd generation 40Gb iPod and play classical music at 320kbs through Etymotic earphones. It is good enough for my commute, but it doesn't compete with playing a CD through my Sennheiser 600s.

I am not sure I would ever want to connect it to my home system, but it is a fine sounding portable player where the headphones and external noise are the worst impediments to a joyful listening experience.

I always play at reasonable levels to protect my ears and am amazed when I sometimes hear other peoples personal music louder than my own music. The - universally young - guys are unlikely to be hearing very well when they reach my age!

Its funny but I have a SOTA home syatem and I find myself using the ipod more and more. I think the sound is outstanding really, that is, with a great set of ear buds or phones and with a good micro amp. I guess to me its music first and the ability to have a couple thousand of my favorite songs with me no matter where I go is what its all about