Was wondering if anyone has any experience with 3-way 770 4Gb with ACX cooling on their X79 Dark?  Can I use PCIe 1,2,3 for the cards?  Have a Caselabs Magnum M8 case which has lots of airflow.  Normally they recommend you leave a space between the cards but with 3-way was not sure if that was even possible?  Is the SLI bridge in the box long enough for PCIe 2,4,6?  What kind of temperature/performance issues will I have with 3-way ACX if they are tight together?  Thanks for your help.  Will eventually be adding blocks but wanted to see how I like the cards first.

I would use slots 1,3, & 6 for 3-way SLI.  That way you have good space between all the cards.  You can't use 1,2, & 3 anyway with double slot cards as once you put a card in slot 2, it will cover slot 3.