Not even in the slightest. I find it extremely silly to get an SLI motherboard and stick an ATi vid card in it
SLI is Nvidia's way of using 2 vid cards at once. Crossfire is ATi's way of using 2 vid cards at once. Both require their own motherboard. They are not interchangable.
If you are getting an SLi mobo, then get an Nvidia vid card. Even if you have to get a 6800GS now (which isn't as good as the 7800GT), then get that instead. That way, if you choose later, you can get a second 6800GS and run them together in SLi.
If you insist on getting an ATi vid card, definitely don't get an SLi mobo. If you want to add another ATi card later, then get a mobo that supports Crossfire.