A 650 won't do it. Approx ~230 watts a piece for the GPU's, plus the CPU. Then all the little things added up(fans, drives, ect...). Then you need to be several hundred watts above that. You can't put a 650 watt load on a 650 watt PSU. An 850... that is acceptable, if it's a good unit.
On another subject. The FX 8320 will bottleneck. As the old FX clips are not good for SLI or crossfire. Tom's tested a 8350 with Radeon 7970's back in the day(vs. an i7-3770K).
http://www.tomshardware.com/reviews/fx-8350-core-i7-3770k-gaming-bottleneck,3407-5.html