You are going to want at least a 430W power supply, and it WILL need the 24-Pin connector ........ Also if you are using a PCI-X Vid Card, make sure that you plug in the 4Pin molex on the mobo, near the back plane ........ Also you will want to use a connector that is on it's own Rail .......... Currently the Intel groups responsible for providing Trade show PC's for Employees are using the:
Vantec VAN-520A
520 Watt Power supply.
This is a known issue with the systems cooking themselves.
Hope this helps yer problem.