Since your motherboard has a PCIE slot then yes, you could run a 9800 GT, you could even run a GTX 690 (space & PSU permitting). PCIE is backwards compatible.
Edit: A Radeon 7750 would be a better option as it's slightly faster than a 9800 GT but I don't think it warrants the extra $30. As ASHISH65 already implied, a lot is determined by your budget.
GeForce 9800 GT $57
Radeon 7750 $87
Radeon 7770 and Antec 450W PSU $141