+1 for a 7970. I would go for a Sapphire 7970 if it were me. As above since you already have a Crossfire 6950 setup I would not really upgrade with the current line up from AMD or Nvidia. That will/might change with the AMD 8xxx and Nvidia 7xx lineup but for now I would not do it you really would not be benefiting from a whole lot going to the 7xxx or 6xx cards. Unless you are having problems with the Crossfire setup itself where you need to only use one card in that case you would benefit from a 7950/7970.