I have a HP p7-1234 with a Radeon 6670 2GB in it. It really didn't improve my performance by much so I'm debating on getting a GTX 650 Ti 2GB with a 400W or 450W power supply. One question was, how will it run with a 1440x900 resolution with games like Battlefield 3. And the other question is: will a PCI-E 3.0 Card like the GTX 650 Ti run on a PCI-E 2.0 slot?
1)Gtx 650ti is good choice for your resolution.it can easily handle games at high settings 2)Pci exp 3.0 gpu will work in pci 2.0 slot as pci exp are backward compaitable and there will no performance loss if you put pci 3.0 in pci 2.0slot 3)your psu is cheap and not good.i suggest get corsair cxv2 430w psu and it is sufficient for your rig.