Re: Ive asked this before
You don't need much. Go to newegg, craigslist or even ebay. I just picked up a 3ghz refurb'd dell optiplex for $60 w/ shipping, so there's a lot of good deals out there.
Here's a basic system from tiger direct that's under $100...
Linky:
http://www.tigerdirect.com/applications ... 96&CatId=6As for power profile, run it thru a NAT or firewall, setup XP pro's remote access thing and you won't need a keyboard, mouse or monitor. Just the tower. Plug it into a good surge suppressor or a UPS, good to go. Run it from a small corner somewhere and just use RA to bang games.