Save yourself a bit of cash and buy two or three 460s instead. ;-)
My existing motherboard doesn't do SLI, only crossfire. It was one of the first to support the Q9450 and at that point there were shenanigans between nVidia and intel. Alas, thanks to my X48 chipset, no SLI for me.
Of course, that could be the perfect excuse to get an X58 and core i7...
However, getting a bit off-topic here :-)