I bought a Corsair GS600 PSU and just realised my 6950 uses both the PCIE connectors. If I want to crossfire another 6950, is there anyway of doing it or must I change PSU?

I just found out about the 7800 series GPU's. I think I will get a 7850. It only uses 1 6 pin connector. If I need to add Xfire, only use another pin. Plus the energy consumption on those cards are very low, even on load.

Most probably have to get a ivy bridge proc (cause it uses only little energy) to ensure the whole rig doesn't stress the PSU with Xfire 7850. I think it maybe achieveable