I have the SR60s. I use them primarily for listening from my Powerbook, but I have also used them occasionally with my iPod Shuffle. The SR60s sound great in both instances. They're not completely balanced (they sound a little "bright"), but for the price point they are very, very good. They are designed specifically to not require an amp. I am completely satisfied with my pair.
From what I've heard about the SR80s, they can provide some noticable difference in quality even without an amp, but an amp is necessary if you want them to perform at their full potential.
If you are choosing between the two, I think it just comes down to what you are willing to spend. The SR60s were at the perfect price point for me at the time, and so it was difficult to justify spending more for the '80s.