MSI RX 470's 4 GB ($199 NewEgg) are 110-120 watts each measured at the wall. I only have two so far, but I got this number from 60 watts system idle with no cards and 300 watts with both cards while mining. So the math is 300 total - 60 system = 240/2 cards = 120. It does fluctuate a bit (280-300), but 300 is the peak. I am thinking I can run 4 card rigs with a 750 watt PS easily, saving money versus those 1000 watt+ units.

The memory clock on this particular model is set to 1650 factory, but I have already successfully increased it to 1850 and am getting 21.5 MH/s stable. It crashes if I go for 2000 (which yields 22 MH/s before crashing), but I think I can work on the settings and voltages to get it to stabilize. I have only had it a day, so I just want to let it run for awhile to make sure there are no other issues before playing around with it too much more.