A more opensource-friendly iPod alternative?

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I love my iPod, and it works just fine under Ubuntu Linux (I can add and remove tracks using Amarok and Rhythmbox without a problem), but recently the 2gbs I'm allotted have become a little cramped and I've been craving a replacement. Now, I could always just get a 4gb or 8gb Nano, or one of those 30+gb iPod Videos, but part of me wonders if I might be a little more satisfied moving away from the Apple brand altogether and trying something different. Perhaps something that'll play more obscure formats? Something specifically designed with a Linux user in mind? Something with functionality beyond just playing music? I've heard the Cowon (www.cowonglobal.com) players are fantastic AND Linux friendly, but what other suggestions might you guys have? Do you have a really cool underdog mp3 player that beats the iPod?