Well, I don't recomment 7 gpu rigs, it's a pain in te ass to make them work...
I'd recommend flashing them you can get 28-29mhs/100w for eth, h97 anniversary, usb risers and a 850w psu.
If you're interested I might have a spare equipped mobo with 5gpu slots, risers and a 470, will decide if I sell or not in a few days (still trying to get my 7th gpu to get recognized on the mobo, I'm close to abandon, but not quite yet!)
I've got msi gaming 5 motherboard. I've heard that motherboard work well with 7 gpus