Which country are you in?
According to asrock the best graphic card that your mobo supports is the 7800GTX. I rekon you upgrade your mobo and stay away from asrock because even though they're overclockable, their PCI-E video card is very limited. I went with asrock at first thinking it was cheap but I got screwed over and swapped it with a Asus P5Q motherboard. My mobo was 4CORE2DUAL-SATA which did not support PCI-E gen 2.0 bios which ment 8800GT cards and up were not supported and I had to flash it to a Gen1 Bios to get it to work which if I didn't have another mobo at home that supports Gen2 bios my card would've been toast.