I don't care if it's used, as long as it works well. And the thing is, all three have their own ups and downs. My current collection of MP3s (mine alone, not including my dad's who will probably use it also) stands at just over 7GB, which will be a major factor in the decision.
The following is based on auctions ending very soon - in the next 12 hours at most.
iPod - 2nd Generation 10 GB Model: Top of the line MP3 player. Fast transfers, great battery life, excellent interface. Unsure of whether or not it can store date files or not. Smallest of the three by far, at 4.0" x 2.4" x 0.72". Very limited space as opposed to the other two options. In terms of value, it's still not as good a price as the others.
Archos Studio 20 - 20GB Model: Cheapest of the three. I hear it works great using Rockbox Firmware. Questionable interface for me - never seen it in action, which makes me hesitate. USB 1.1 interface - not the best, but that's not too big of a problem. Battery life is unknown. Bigger than the iPod at 4.5" x 3.2" x 1.3". Uses a drag-and-drop system and can be used as an external HD. *Very* easy to mod, in the case I decide to upgrade the hard drive.
Rio Riot - 20GB Model: Priced in the middle. Great internal interface, but only uses Real Jukebox for transfers. USB 1.1 interface also. Great battery life - at 10 hours from what I've read. Not capable of being used as an external HD. Also has an FM tuner. This thing is a brick, however, coming in at 5.5" x 3.75" x 1.25".
So, the question at hand is which one to go for, as the time ticks away. I hope someone can help me with the comparison and chime in, as there's little time remaining. Sorry to bother, and thanks in advance.
Edit: Well, as expected the iPod jumped in price. I guess that's out of the question.