I tried building my own multi-screen computer but I got a lot of crashes etc.
I finally broke down and bought a really nice Four Monitor system and it runs great.
Here's what I got and I'm very happy with it:

Multiple Monitor Computer

Quad Screen Multi-Monitor Display

It pretty much looks just like this following video, except that the bezel is black on mine....

Multiple Monitor Computer Video

It all cost about $2,500 with the computer and Quad LCD Display.
I hope that helps you out!