Actually you can SLI them. I'm currently doing it with success. My 9800GTX is the primary and my 9800GTX+ is the secondary. My drivers came up funky for a few restarts but for some reason XP went "Oh wait. Sorry, bud, I see the card isn't an 8800, my bad." My bridge was positioned wrong which probably had something to do with why my drivers came up weird after installing the second card.