As per this annoyingly white chart your PSU is a Quad Rail, meaning that your 2 VGA lines each put out a max of 40A. Mind you, if each rail was max tapped, that would be 1560W, and your unit is only rated for 850W, so I doubt you can run both VGA rails at 40A simultaneously. Also sharing the load between 2 rails would lower the stress on the rails, and improve efficiency, and thus lower heat production. My CM Silent Pro Gold 1200 is a monorail 98A: So this unit can provide up to a total of 98A for all 12v sources. Getting back to yours, your spec sheet says 25A MB, 25A CPU, 40A VGA1, 40A VGA2. So assuming that your mobo and CPU both don't suck up 25A each, whatever capacity remains will be shared with the VGA rails, up to 40A per rail. Even at 25A + 25A + 40A = 1080W @ 12V, that would be about the max burst output from the PSU, and boy would it get hot. So you need to calculate the mobo and CPU amperage draw is to determine how much juice you have left for running GPU's. EDIT: As per another white chart: at max load, each VGA rail has 18.79A available to it, with 11.74A available to CPU and MOBO.