A lot of people were complaing about their framerates with X19xx cards. The game isn't optimised for them, and even less so for Xfire or SLI - people have reported only marginal games with 2-card setups. Still, it's a fast card and no doubt they'll slowly tweak a lot more performance out of the game, and your CPU is fast as well, so I don't think it's worth upgrading if you're ok with running the game on medium settings. What might be worthwhile is another 2GB of RAM, this game needs 2.1GB on its own I believe (total though, not just unpaged, so it should run on yours but would thrash the drive a bit, and 2.1GB is the maximum, it's not always usign that much).