For an Awesome DIY power supply Search on ebay for HP Dell DPS-600PB

They are 12v 475 @ 575w. you can normally score them for under 20$ a pop, I got mine for 12.50 each.

For the DIY part, RCGroups has a Tonne of info on wiring them up. Just google search HP Dell DPS-600PB Mods

here's a Very good write up on running them in series.

http://www.tjinguytech.com/my-projects/diy-24v-47a

here's the same guys site to actually turn the supply's on.

http://www.tjinguytech.com/my-projects/HP47A

I also Highly suggest the Fan step down mod, the fan's aren't stupid loud or anything but for what its worth to jumper 2 more pins and it steps up the fan speed automatically when needed.

here's what a pair of mine are doing, Motion Simulator power for JRK motor controllers.