I have a 550W PSU from Chieftec. It has three 12V rails, 18A each (3×18=54A). Now I want to buy a Geforce GTX 260 that requires a 500W PSU and 36A power on 12V. I suppose my PSU will be fine, these 12V rails should self adjust ?? Funny thing is, the PSU only has one PCI-E cable with two 6-pin connectors.
http://www.chieftec.com/smart-power.html
http://www.chieftec.com/smart-power.html