posibble

i need to chose from 7750 or 640 possibly 7770 if under Rs 8k.i have a Asus P5kpl-AM/PS and Core 2 Duo E4500 @ 2.2 Ghz:cry:,i want to overclock it also upto 2.8,want to know how much fps difference i will get in shogun 2 and bf3.having a stock fan, 450w psu,4 gb ddr2 1033mhz. i need to play bf3...