A single GTX275 will do the job better in most cases... plus it has better driver support, better technology (55mn vs 80 or 65nm of the 8800) which means it's more efficient, plus the 8800 in SLI's performance depend on the game you're playing and in some cases will scale baddly... GTX275 will even outperform a GTX280 which is almost as fast as 2 8800GTX in SLI!