your psu is only 80plus bronze, and looking at the 80plus certification, at full load you're pulling 1025W from the wall and pushing 851W for an efficiency of 83%.
at those clocks and voltages, you're probably drawing around 220-230W on the 7970s, and around 125W on the 7850. so your GPUs are probably drawing roughly 575W.
factoring in the 790W you've measured from the wall, at 83% efficiency measured above in the 80plus certification, your system is drawing 655W. so the GPU power estimates there are probably pretty close, if not a little bit inflated.
your system power supply is able to sustain 851W output, so you have plenty of headroom for your current load. you should only be concerned if you start drawing around 1000W from the wall.
at those clocks and voltages, you're probably drawing around 220-230W on the 7970s, and around 125W on the 7850. so your GPUs are probably drawing roughly 575W.
factoring in the 790W you've measured from the wall, at 83% efficiency measured above in the 80plus certification, your system is drawing 655W. so the GPU power estimates there are probably pretty close, if not a little bit inflated.
your system power supply is able to sustain 851W output, so you have plenty of headroom for your current load. you should only be concerned if you start drawing around 1000W from the wall.