Use the Newegg PSU calculator. It overestimates to be on the safe side but is a pretty good lead to go by. It recommended 564Watts for my configuration, but I use a lower power Micro ATX board. Should I have had two 6950's instead of one, it recommends 864+ Watts lol I seldom believe in going beyond 500W. I will figure out how to build a super gaming machine using 500W or less in most occasions these days, as there are a ton of low-power options now, compared to the days of old. I have never needed too much beyond 500 watts in the past, no reason I should start now. My next two cards will be the low pro/ low power cards made by AFOX. Look up AFOX's 6850/ 7850 LP cards. I also only use Micro ATX boards, which are lower in power consumption. This last time around, I went with a 125W CPU FX 8150 8 core. My last CPU was a 95W Phenom II Quad. For the sake of CPU longevity, I decided to go with a high power/ watt CPU. I had the 6950 already and will continue running it until I have the option to save, budget and cut power elsewhere. In the future I imagine things will all go Micro ATX/ Mini ITX with the whole tablet smartphone market making micro chips super popular and affordable. I hope this is the case.