Assuming your system is capable of running the gpu, you need a graphics card that is capable of running 3 monitors. Either nvidia gtx670 or higher or radeon hd57xx series or higher. Anything below these will require 2 gpus not connected in sli or crossfire. If you list your system specs, what make and model psu, as well as what and how many monitors (models) we will be able to give you a better idea. Also, are you trying to run 3 separate desktops, or one big screen (eyefinity)?