Triple monitor setup on two GPU?

[Ash Cloud]

Currently i have a GTX660 2GB running a single 1080p monitor, im planning to get 1 or 2 1366x768 monitors which will just be used so i can have extra windows open. I will be playing games only on my 1080p monitor and i will do video editing and use my other monitors to output the preview window. My question is should i buy another cheap GPU to run the other two monitors, if so can you recommend me any cheap GPU, or should i run all three monitors on my GTX660.

 

[Gam3r01]

The 660 should run everything just fine. Im running 2 monitors on an old 7750 2Gb DDR3 model.