ihave amd fx8120, asus m5a97 r2.0 mobo , trans cend ddr3 4 gb 1333Mhz ram, cooler master Gx 650W SMPS, and nvidia geforce 8400gs graphics, . i have experiencing sudden frame rate drop from 55-60 fps to 7 -10 fps while playing assassins creed 3 and battle field 3 and crysis 2. iam gonna buy gtx 660 or 660 ti . suggest me good one to go for ti one or non ti one . is my cpu is bottle neck?