As another option, buy one graphics card for gaming, and a cheap second card to attach the two non gaming monitors.
Good idea, if your board has 2 PCIe I would get a 7770 for around $125 and then a 6450 for around $30.
The main monitor runs off the 7770 and is used for gaming, the other 2 monitors are plugged into the 6450. In this model you are not using eyefinity or corssfire you are simply using multiple GPUs.
This would be cheap, easy, scalable, and work very well for productivity like having WORD, EXCEL, and ACCESS all on thier own screen at one time.