I think it all depends more on the experience you want rather than just the ability to play something. I still tend to prefer the Apple GUI when it comes to the music players (although I hated iTunes with a burning passion). That said, I have used a Zune (don't much like that GUI but I know people that do), and now Android (stock and double twist) and all are just fine in terms of sound quality. If this is all you are looking for I feel you could get most any mid-high end (maybe even low) Android device and be perfectly happy. The nice thing with Android is you can download other music players, although I haven't played with this much (outside the realm of double twist).
"A dog is the only thing on earth that loves you more than you love yourself" - Josh Billings