In my experience aros works on ANY x86 computer, so long as you have the following easy to find on ebay parts :
Soundcard = sblive Networking intel pro 100 video : nvidia fx (550,650) series.
To me its worth 30 or 40$ in cheap easy to find parts to save yourself the hassle. Yes some onboard video/sound/net cards work, but in my experience its not worth the hassle trying to do that, just get any pc with 3 pci slots and you'll be fine with these easy to find parts...
My current machine is a 2ghz machine. Its fine for most everything (games, browsing, writing, whatever my day to day needs are)
AROS on PI will be nice, but remember, I don't think 700mhz will be beefy enough to play classic games. I think performance will be usable on native apps but slow on anything emulated.
Steven