I have an PCIE slots,no agp
Then you'll be able to use any PCIE graphics card, pcie1.x or pcie2.0. Pcie2.0 is backward compatible, so no problem there.
If you plan to run games, common choices include 3850 8800gs/9600gso, 9600gt, 3870, 8800gt/9800gt, g92 8800gts/9800gtx, 4850, gtx260, 4870, gtx280, 9800gx2, 4870x2, in ascending order or performance. Your old cpu will bottleneck higher end graphics cards, but it shouldn't be too severe until 4850.