7 to 8.5k

I am planning to buy a decent GPU for max 8k, my PC configuration is: AMD Phenom II X4 B45 Processor @ 3.00 GHz 6 GB RAM Gigabyte GA-MA785GM-US2H Motherboard Cooler Master RS-460-PCAR-A3 460W Power supply I want to be able to play current games like MW3, BF3, Crysis 2, fifa 13, Arkham City...