The Gtx 260 is ok but get the Evga 216 version if you want to go nvidia way. The 4870 is the best single gpu on the market. In a dual gpu environment (crossfire/ sli) nvidia 280's win if you go to
Tom's Hardware: Hardware News, Tests and Reviews and look up the latest gpu charts it may help you decide
Btw ignore the last comment from third shift I think he just read the first post non of the details