Your board has a PCIe 16x version 1.0a slot. It will support any card that is out with the exception if the card is version 2.1 there might be some issues. The best cards on the market are HD5970 and GTX480. Both cards are probably an overkill for your system, are expensive and require big PSU´s. Based on what resolution you have on your monitor I would recommend either HD5770 or GTX460 for your system.