Suggest me a cheap graphics card that can play wow and sc2

Wow, you got a great components there...
So, why do you plan on Corsair HX1000 if you just want "cheap" graphic card?
If you really want a cheap card then 500W PSU is just more than enough...

You can add 3x HD5870 with that PSU.
Or MANY "cheap" HD5670 or GT240, well that's if you has MANY pcie slots...