God could you imagine how much power 4X 4890's would consume? That would be a heat pump sufficent to heat your house in the winter... 
Actually although GPU's are hotter than CPUs, they also have higher thermal thresholds, so a good 320 radiator would be fine for 4 GPU's a Core i7 920@4Ghz needs its own 320 radiator by itself.
Coupled with a PhII 955 or such 4x4890s could probably run on a Extremely efficient 900 watt possibly 850, with no other extra peripherals. Although I'd run at least a 1000watt to stay in the sweet spot of the PSU's efficiency curve.
I've run with a i7-920@4GHz, 3x4890s, Raptor, SSD, 2 pumps, and about 10-12 fans and I pull no more than 750 at the wall at full CPU and GPU load via OCCT.
Also Sapphire also did a Similar setup with the 4870 Atomic but I believe it also had a CPU block in the pre-made loop.
I say boo to pre-plumbed loops they usually suck.