Arg, here we go again.
You can game on three screens with your curent setup using
SoftTH. However, you will have to run in non-SLI mode and thus one of your 8800s will go unused. Using this solution (which seems to have limited compatibility), you should be able to game at 5040x1050, assuming your hardware can push those pixels. This solution allows for bezel adjustment.
If you get a TripleHead
2Go, you will be able to game on three screens while using SLI to drive the setup. The max res will be 3840x1024. The max triplehead res will be 38040x768. You will not be able to run your monitors at native resolution, nor will they be scaled to another 16:10 resolution; they will be scaled to a 16:9 resolution or to a 15:9 resolution (3840x720 is also available). There is no bezel adjustment with the TripleHead
2Go.
If you wait and get a Digital TripleHead
2Go, all of the above is true plus you will have the available option of a 3840x800 resolution, and everything is run through DVI. Bezel adjustment is a feature of the Digital TripleHead
2Go.
For the either of the TripleHead
2Go solutions, implementing treplehead in games is a hell of a lot simpler. SoftTH requires modified files in each game's instal folder in order to run at triplehead, and the internet is full of people trying to get it to work. It also comes with a framerate hit from syncing the output of two video cards. The Matrox solutions' only framerate hit comes from the fact that you are running at a higher resolution.