I HAVE A XFX 780I AND 3 8600GTS'S. CAN I GET ANY BENEFITS OUT OF A THIRD GPU. CARD 1 AND 2 IN SLI. EBAY 3RD CARD OR PUT IT IN RIG?
What about ebay all your 3 cards and get a single powerful card like GTX460??
You can't use 3 8600GT's in SLI,you only can use 2. The only cards that support 3-way SLI are 8800GTX,9800GTX,and GTX 4xxx series. However,even if you could,I wouldn't have recommended it because 3-way SLI doesn't scale as good as 2-way SLI,so in most games the difference between them isn't much.