Alternative Video Card for Gaming?

I have NVIDIA GeForce 6150SE nForce 430. Can anyone suggest a good alternative Video Card thats good and cheap. A video card for games like CRYSIS, Assassins Creed, Etc.|||I am using an EVGA gt 220 1 gig ddr3 nvidia card. I play online games and it works fine for me. Got mine form fry`s.com for 75 bucks. There would be a substantial difference from what you have now. Must have a pci-e slot on motherboard.