Anymore to do multi-monitor setups you do not need anything really fancy, just a single graphics card that supports EyeFinity. This means looking at AMD Radeon cards that support triple monitor output or more. I put one of these in one of our office computer, the AMD Radeon HD 7850 and the card is tremendous! Not only can it run three or even more full 1080p monitors at once, but it can do so while drawing half the power and running much cooler than the similar range nVidia cards.
I've always been a big fan of nVidia, I've used them in the greatest majority of my builds, but this latest generation of graphics cards from AMD offer such wonderful performance while running so amazingly efficient that I am thoroughly impressed.
What you will need for this kind of setup is going to be an AMD Radeon HD graphics card that supports EyeFinity. You will also need a decent power supply to ensure you have enough to run all your additional hardware needs, usually 650 Watts or more. Then you need to look for the monitors that have the right connectors for your display outputs so that you can connect everything up. True, you can run multi-monitor outputs by putting in dual graphics cards or even more, but you then are introducing more power draw, more heat, more noise, and requiring specific motherboard requirements for running multiple graphics cards. My recommendation is a single card with EyeFinity.