Depending on the resolution I'm betting you need at least a 980ti to drive three screens at any meaningful FPS.
Why not get one of those giant samsung extreme widescreen ones? I think that combined with TrackIR would make a wonderful drivingsim-rig. You also get rid of the bezel annoyance.
Something like this maybe: http://www.samsung.com/us/computer/monitors/LS34E790CNS/ZA