I have a 250w power supply that came with my case. I also have 3 200w extra ATX supplies and 1 150w AT. I am currently set up with a 900MHz Athlon I have so far only been able to get to 1GHz. I have a 72w Melcor TEC that I want to run on separate power, because my checking around different sites indicates that Athlons are tough on power. I am also currently setting up a watercooled system, as air cooling(GlobalWin VOS32) is not improving matters.
By the way, thanks for the sites. The info was just what I was looking for. Much appreciated.