I've got one system with an 1100W PSU and a single 6990 GPU. There are 2 spare x1 slots if you want to rig up a couple more cards, depending on the cards you might need more PSU for that, though. There are only 2 6-pin connectors left and the 6990 uses like 475W in overclocked mode.
The 2nd system has 2 6990's on board and is in an ATX full tower decked out with a ton of fans. There is a spare x16 slot if you want to connect another card. This system has a 1500W PSU.
Both systems come with a CPU dummy plug. All the GPU's and the entire 2nd system are covered under a warranty from the computer manufacturer.
Make an offer for one or both in bitcoin, paypal USD, dwolla, or ACH/wire transfer. Items ships from Florida. I have FedEx and UPS shipping account with discounted rates and can get you a shipping quote at your request.