i will buy corsair hx650, can i run 7850 crossfire on it?
You WILL be fine and not even pushing it, the hx650 is gold rated and can support 4 6pin pci connectors
1 78750 uses on 1 6pin pcie connector
you can crossfire and OC your cpu without any problem,
PS: I saw your 3770k price in india thread, I got my hx650 for rs.6500