Originally Posted by Arizonian
I've read the Corsair AX1000 is two 500 watt psu's in one casing and each have their own 12v rails. Not the best idea from some posts to put two 580's on since they work independantly of each other.
Just to be clear, the only Corsair AX PSU's available are the AX750, AX850, and AX1200, which are all single rail unit. Corsair, currently, does not have a 1000W unit under the AX line. The PSU you are referring to is the HX1000, which is comprised of two 500W units. While the HX1000 is a decent/mediocre unit compared to modern day alternatives within similar price brackets, it can still hold its own very well when handling two to three high end GPU's.
As an FYI to anyone who is wondering what kind of power draw to expect, my sig rig with two overclocked 580's while benchmarking and gaming at 900/1800/2200 at 1.1V never hit 800W. It would fluctuate between 750-790W, depending on the benchmark or scene in a game. These high consumption numbers were done with Crysis, 3DMark 11, and Heaven Benchmark 2.5. Interestingly, as intense as Metro 2033 is, the power consumption numbers were lower, hovering in the 650-700W range. And, all tests and gaming were done while powering 6 mechanical hard drives of varying speeds and sizes, as well as 4 cathode tube lights, 6 Gentle Typhoons, 2 140mm Noiseblocker NB-PK3, and a Scythe fan controller.
Keep in mind, all figures are taken from the wall, before efficiency is taken into account. As many have already stated, a quality 850W PSU will be more than qualified to handle a pair of 580's, even when overclocked; with three 580's being well suited on a quality 1000W. If you are building with a Sandy Bridge setup, you can be sure to see even lower power consumption figures (depending on the overclock, of course).