What do you mean by 64bit card? If you are talking about the memory bandwidth of the card then yes it will be utter crap. It depends on the resolutions that you want to play at and the detail settings. Also for your CPU i would suggest a HD5750 or HD5770 (both 128-bit width but have DDR5 instead of DDR2 or 3) before it becomes a bottleneck for your system. If you are serious about gaming avoid any 64-bit wide cards.