I just bought a monster server machine to run as my MythTV machine. It's a dual 1.4 GHz Xeon with two gigs of RAM and 288 gigs of RAID storage. Nice!
Servers on eBay seem to be inordinately cheap. I guess for just about every business, the whole point of a server is it's important to the business. So people don't buy them second hand. Which means cheap for people like me who are willing to buy second hand.
So this is going to be my MythTV server, sitting in a cupboard somewhere, while my front-end will be a silent, no-moving-parts diskless Via EPIA machine. Should be a rather nice setup!