Hi. This might help with knowing what how much branded (Seasonic, Enermax, Coolermaster, etc.) power supply is the best for your needs. Its calculations include most current graphic cards including SLI or Crossfire Setups and CPUs. Take note when adding another video card in the selection. Also, take note that you read the legends at the bottom of the page to give allowances to the calculation. My non power supply's amperage seems to be better than some branded power supplies of the same wattage 650W which is enough even for an SLI according to the calculator. But I don't really believe in SLIs or multi-cores coz' the bottleneck there are software developers who includ game developers. Nothing beats one fast chip, though multi-cores and SLIs is where its gonna' head off to. I guess the best would be better development softwares that take advantage of any additional cores or dual cards as it comes out, not after a few months or years. Have fun with the calculator, it can be used, by subtraction, how much a certain model compares to another. It even includes calculation for when you overclock (not recommended, just get a faster component, its wattage is way up there). The link is:

http://extreme.outervision.com/psucalculator.jsp