I have a 680i mobo and 2 8800gtx GPu's and a 22" monitor. I was thinking of buying another 8800 gtx, but was wondering if i would get any better performance on a 22" monitor worth the purchase of the new card. also i think if i do a 3 way Sli on this mo bo all three cards run at 8x pci instead of 16x ... is there enough preformance upgrade worth the purchase ???
It all depends on your resolution. I'm assuming your 22" runs at 1680x1050 or 1920x1080 - At those resolutions you should be set with just those two 8800GTX's, but If your looking into running multiple monitors, then a third one will never hurt.
In short, a third 8800gtx may give you some of a performance increase, but you've already for two pretty powerful cards there