|Below is a link to the only 650W I found from that brand. The power supply has 2-12V rails. Each supplying 25A. One rail will feed the board and CPU. The other, the graphics cards and all the other 12V hardware like drives and fans. |
Two 5850 cards draw 27A by themselves, leaving nothing for the other hardware. IMO, that PSU isn't going to work with a pair of 5850s.
What motherboard are you using? Can you even run Crossfire?