Falcon1 wrote:
600W from the wall outlet? Then, that's before the PSU efficiency. 800W PSU means, it can deliver 800W. It might be draining more from the the wall outlet.
Here in Germany, electricity is quite expensive. I always recommend smaller PSUs, so that it works with optimal efficiency. (Typically at at least 50% load)
850 actually seems just right for crossfire. I peek at around 720watts from the wall when I hook up a kill-o-watt meter when I max my dual gpu 7990 and pin my i7 at 100% all cores. I run a 1000watt psu
I would also stay away from the Xeon