How much power?

The 7950 practically sips power. I would go with the lower estimate and get a 750w PSU

About 650W.

Total power draw would actually only be around 450W, but a 650W will be the most ideal PSU that will have all of the connectors for the GPU's.

I would say 800W to be sure or if he wants to overclock the cpu and both gpu and add some fans.
But i have a question. Why 2 7950   ? one is not enough?

2 for the future. Oh and yes, I will overclock it. Not extreme tho.

extreme outervision's PSU calculator's giving me 608W, assuming you OC the CPU to 4.2ghz at stock voltage. but considering the site's tendency to over compensate, you could probably run it with 550W if you OCed nothing at all.

but assuming you do OC, 650W is a safe maximum

700 sounds right if you ever want to add more to it.

Ok then, if you say so i believe you.

Best answer selected by Gxavier38.

Thanks guys.