The last time I tried SLI does work in WoW but not very well. The biggest problem for me with 2x8800GTX was that every time I alt-tabbed it would drop the FPS a few. After 4-5 tabs it would drop down to unplayable level. The only fix was to kill the client and restart. It is much better to get yourself an 8800GT (512MB) they run around $250.

Ziran