Graphics card holding me back

I just built a super budget gaming pc with some cheap parts and leftovers from other builds and friends scrapped computers, but when I try to run games like Far cry 3 at anything about medium i see serious FPS drops, I know it's the graphics card, but i was wondering if there was anything in my system holding me back. I was thinking about getting a GTX 650ti or GTX 660, I'd like to run Far cry 3 and skyrim and max settings but i also dont wannt spend more than around $200 on a card. Any input would be greatly appreciated

System Specs
CPU - AMD Phenom II X6 1045t
Memory - Corsair xms 8gb ddr3 1333
HDD - some 500gb WD drive (blue i think)
Motherboard - gigabyte balls edition
PSU - ultra 600w
Graphics - GT 630 2gb