Ok so I've had experience with this with my own setup so i thought I'd share how I did it successfully.
Step 1: What is needed
You basically need to have a dual card setup that can operate in SLI mode. This is because the threee monitors you will need to connect need to be shared between the two cards. You obviously need the screens x3. Windows 7 is a good start and the latest Nvidia drivers. Also note that Surround is only compatible with GF200 series and higher.
Step 2: What do I do?
Ok so computer off and you need to connect two DVI cables from your first two monitors to your 'main' upper slot gpu. the third DVI cable from your third monitor connects to your second card. Also note that when using your Nvidia driver software to setup you will be shown a diagram of the correct connection of your 3 montiors. Now that your are connected up, boot up and start your Nvidia drivers software, this can be done by right clicking your desktop and selecting Nvidia Control Panel from the drop down menu, you can also access the control panel from Windows 7's control panel menu. Once nvidia control panel is open you need to go to the 3D Settings List on the upper left and click on 'Configure SLI, PhysX, Surround'. To configure surround you need to run the wizard by selecting the Span displays with surround button and then clicking on 'Configure' located directly underneith. You will then be presented with the diagram I mentioned earlier that describes the correct connections for your DVI cables from your monitors to your gpus. If everything looks good click on 'Apply'.Ok, next you need to line up your screens so that they are in order of eachother. This easiest way to do this is by clicking on 'Identify' andmatching your screens to the diagram the wizrd is showing, so if monitor 3 shows as the left monitor when you identify, but the diagram has it on the right you need to match up by moving the monitor in the diagram to the far left to line them up. next you can choose whether to have modded resolutions added that correct bezel compensation or not and then basically that's it. Immersive gaming Baby!!