That TR2 750w power supply is kill your computer bad.
For a Crossfire 6870 rig I would go with 700-750 watts.
Seasonic, Corsair, PC Power and Cooling, XFX, Silverstone, Enermax and Antec are all great choices.
Where are you buying from? I will check what the best deal is if you post me somewhere to look.
I'm buying my stuff from the store tigerdirect but if they don't have it I'm ordering it online from their website www.tigerdirect.ca