Thanks very much for the quick reply!
I went to the CoolerMaster website where it has a PSU calculator. I entered my specs and it came back with a 1200w PSU required! I did think that was a bit excessive!
1200w might be required to run four but not two.
We all know that the GeForce GTX 480 is not exactly the most efficient GPU on the block with its 250W TDP. Four of these when peaking can already consume a full KW of energy. Add another 130 W for the processor another 40 for the chipset and then some more for peripherals and 1200W really is something you need at minimum.