You still wouldn't need it (you could run 640*480 and it would still work, just being very wasteful). If you have a budget that allows you 3 780 ti's and the monitors to go with it, then by all means go for it and more power to you. While we are on the subject of power though, make sure you have at least 1k watt PSU if you do plan on running 3 780 ti's, you could get away with 850 but if you are spending that much on GPU's then spend 60 more bucks and make sure they have juice to spare.