Can I ask if you are going to air cool these three in a case? And if so dare I brave the anger of the ASUS gods and suggest that triple SLI in a case might actually be better with the reference cards.
I had 2 680 DCuIITs and had them in a case with great airflow but they vent all the heat into the case around them and very quickly saturate the environment in your case with very warm air. The reference design vents out of the case and with good airflow I think will overall work better. I had to take the 680s out onto a bench table for them to prove the benefit of the cooler design.
I find many of the reviews confirming the marketing claims for these cards are running them outside of a case too and think this is a bit misleading to say the least.
This is my personal experience and I did not collect hard data to back up this impression but I'll post it up for you to think about....