You should be looking at total pixel count when you look at which card you want for your resolution and tinmann is correct that you will definitely want the EVGA GeForce GTX780 SuperClocked w/EVGA ACX Cooler for your triple monitor setup. The 660Ti is far behind even the HD 7970 when it comes to that high of a resolution. The 660Ti is about three levels below the 780.
Does EVGA has the best cooler for the 780? I do notice temperature spike from 40 to 75 in my 660ti in surround mode. I am definitely for getting a 780 card with good coolers.