I am not familiar with using nvidia surround but a quick search says that your motherboard needs to be sli compatible, unless you have the gtx 295, 590 or 690.
Unless you are referring the the 3D surround which would require 3d compatible monitors.http://www.geforce.com/hardware/technology/3dvision-surround/system-requirements
As for using 3 monitors it really is up to you, I have to 660ti and have 2 hooked up to dvi ports then the third (a tv) to the hdmi port. What size monitors are you looking for? By watching sales I have found 23" monitors in that range. Microcenter.com and newegg.com both have them for around $130