Almost every card is compatible with your board but make sure that you have enough power pin connectors. If you don't have enough power connectors get a molex to 8pin connector or molex to 6pin connector whichever is necessary.
If you want to stick with Radeon you can get yourself a HD 7770 $150 to $7870 $190 - $250 for higher quality gaming get a HD 7950 $310 or HD 7970 $380-$460.
If you are planning to switch to nVidia GTX 650 $170, GTX 660 $220 for high end games GTX 680 $450-$500
NVidia cards are expensive but has slightly better performance and consumes less power. AMD makes up for that by its low price and performance of the GHz Edition cards.