I used to run 5760x1080 on a single 670, and dropping settings down to medium meant my FPS never dropped below 60.
It's actually quite disorientating playing at 5760x1080, so I'd opt for a higher resolution screen rather than triple screens but it's up to you of course.
Setting the screens up on a single 770 is easy though - plug two in to the DVIs and the other one in HDMI, activate Nvidia surround and it should work fine.