In the previous thread, you were suggested a few GPUs. The new GTX 760 and 770, for sure. You could also consider the Radeon HD7870 XT or HD7950 instead of the current HD7970.
Any of these 4 GPUs can handle 3 displays.
It is very important that you also consider the types of connections your displays use (VGA, DVI, DisplayPort, or HDMI). For 3 displays, you need to use 3 digital connections (DVI, DisplayPort, or HDMI) and one of those must use an Active DisplayPort adapter. You don't want to use any VGA ports or adapters.