Thanks! This is a z77a-GD65 board, so I may try adding a 7th card for the hell of it. I've got 16 more on the way already. 6mh/s, from one rig? Have to try 

I have a pair of EVGA supplies under this one, a 1300G2 and a 1000G2. The 1300 runs the board, riser cables, and three cards, and the second 1000W runs three cards and a SSD. I'm not exactly sure of power draw yet, but I'm sure it's brutal.

I guess 290's have to use signed bioses, or at least they did? Seems someone may have found a way to load voltmodded bioses to 290's, certainly keeping an eye on that thread 

I plan on either buying a kill-o-watt on my way home from work, or swapping in one of the 1500W evga supplies I have with the built in load meter if I can't find a kill-o-watt. I'd rather not mess with that, since the "supernova" software only runs on windows...