I believe you have a pci-e 16 1.0 slot. We are now on pci-e v 3.0. While the cards are backwards compatible what you are losing is lane speed as it has gotten wider and faster with each revision. That said, your psu is good enough to power the most powerful of cards. I believe the slot and your cpu will be what bottlenecks your gaming experience at times so for your particular system I'd try to find the best price to performance price point as my rate limiting factor and the GTX 650 Ti is a great choice. It's compact, low psu requirements (400W) and it should work just fine. I was going to recommend the newer 750 ti but I've had clients who had compatibility issues as it is a rare card that draws power from the pci-e interface itself and your mobo may or may not be able to do that. I've used the 650 Ti myself and it can max out games like bf3 to give you an idea of how strong it is for a sub $150 card.