hi guys, my rig as follows mostly medium settings, with some lag in huge army battles, i wanna know if i upgrade my gc to GTX250 / 460 or 5770 issit sufficient? can the proc handle it?

athlon am2 x2 4200+
abit an52s
kingston pc667 ddr2 1g x2
sapphire hd3650 256mb ddr3
xigmatek nrp-pc502 500w