660 vs 650 ti vs 7850

I need help on deciding what GPU to buy. my full system specs are; mobo Asrock fm2a75m-dgs CPU amd a6-5400k oc'ed to 4.0 ghz psu corsair builder cx430 w  6gb of RAM HDD seagate barricuda 7200 rpm 500gb OS windows 7 home edition 64-bit

You should NEVER get a dual-core APU, as it will bottle-kneck your GTX 660, 650ti, and Radeon HD 7850. I Would say go with a better CPU, haswel core i5, ivybridge i3 or FX 4100 and up, preferrebly intel becuase lower power consumption, heat, and MUCH better sing core performance, along with just better performance. If youre on a really tight budget, just dont get a GPU, as you can always buy a top end APU and add a hybrid setup later. And the GPU, GTX 760 is th same as  a 670 performance wise, and costs the same as a 660