I have a Benq XL2720T monitor. I have gtx 580 feeding it at the moment. I'm thinking about switching for gtx 780 and getting two more displays, to make a surround system. But I don't know if two extra monitors will display image with 120hz. The main one connected with dual-dvi sure, but the rest?
More aboutgtx 780 vision surround 120hz monitors
It will do two just fine, but you will need to use an adapter on the display port. I don't know alot about connections and the like but I gather its an expensive one to make it work, someone on the Nvidia forum had trouble doing it off one card.
To really take advantage of the 120hz, you may need a 2nd or 3rd 780.