Also, you're increasing power consumption by more then what's necessary. Price/Performance has gotten better, by far, but it's still not quite there yet.
Also, SLI/Crossfire isn't suggested unless you're running a higher resolution. 1680x1050 and under, you're just dandy with a single card solution. But if you're running 1920x1080 and higher, then running a dual card solution would be a good move, moneys permitted.