As far as I'm aware, the EVGA 850w P2 is perfect for this job.
480's have 6 pins, correct?
http://www.evga.com/Products/Product.aspx?pn=220-P2-0850-X1
Maybe I'm misunderstood and it literally just means the cables themselves, but it looks like this has 6 total pcie/vga connectors. Can someone confirm?