I have 4 5970's in a single rig, which is 8 GPU's. Uses approximately 1040 watts at the wall, using a single PSU (rosewill lightning 1300W. 80plus gold). Using Windows 7 x64, driver 11.12, sdk 2.1, bfgminer 2.7.4, phatk kernel, vectors 2, worksize 128, 10 intensity. Having no problems once I weeded out the bad riser and found one of the GPU's doesn't like a certain memory range. Core speed of each GPU is fine tuned and maxxed, any higher and it causes driver resets. If you're looking for a picture of the physical rig itself, it is the one in the lower right in the second picture.