450w to around 650w should be enough (give or take a fairly efficient 80+ rating), the two pci-express 16x slots should be able to power them since they don't have any soldered 8/6pin power. Why would you spend $230 on each when you could basically spend it on a more power gpu instead? if you don't mind me asking @Thermite
Well each card does have 6 display ports so it's a good idea in theory until you see the price, that would be $460 on the graphics alone. With that kind of money he could get a board with more PCIe slots and get three or four low end GT cards and still come out cheaper.