ya its quite good, a better card is a nvidia 7800gtx but check some of these benchmarks if you want a good comparison of quite a few new cards. personally i think ati is useless but hey, thats just me. i was gonna get a 6800 ultra but then they released the 7800 so i prob gonna just get that. oh yeah is it a pci-express 16x or an agp 8x card?
benchmarks are on toms hardware heres the link, its got quite a bit of info.
right now AGP and PCI-E are about the same in performance unless you go for Nvidias SLI which then almost doubles performance. if you upgrade the whole computer get PCI-E coz they newer and prob will take over in performance in the months to come.