no problem, you'll be happy with the 4870, should be able to play any game out right now. only reason I'm not running my 2 right now, is I couldn't stand the fan noise when run at full load, not jet turbine loud, but loud enough, switched back to Nvidia and running a GTX 285.
those Sapphires are the ones that replaced my Reference design versions, the best ones for fan noise (low levels, and still good for heat dissipation) are the Sapphire Vapor X models, but those should still be pretty decent.