Two 6870s in CF won't be very much faster. The difference is so small you're not going to notice it. The 6900 series cards will be out next month to boot. Even then performance probably won't be too much more than 25% extra over the 5870 but we'll see. Wait and see what the 6900 series brings, but I don't really see a point for you even wanting to upgrade unless your running 3 1080p monitors in eyefinity.