This is what I've come to the conclusion to so far:
[list]triple head 2 go just emulates ONE large monitor
you don't use any of the GPU horsepower from the auxillary GPUs the Center GPU is the only one being used.
DX9 / xp limit the resolution to such the extent that 3x1920x1200 is not possible.
TripleSLI might work but that doesn't use GPUs for their respective monitors - you still have to use triple head 2 go and use one large res screen.[/list:u]
1) In order to run a 3d game it requires directx to think it is just one large monitor. TH2G can't do 3x1920x1200 because of hardware limitations of the TH2G box.
2) Using tri-sli would require using a TH2G box.
3) 3x1920x1200 is not outside the limits of DX9 nor XP. It's a limit with how you have configured your setup.
4) Tri-SLI won't work with your cards because the FX3700 does not have the dual connectors on each card for the tri-sli bridge.
Your only real choice with this setup is SoftTH and using 2 of the 3 cards. The third card is useless. Main card will do all the work while the second card will merely overlay the rendered area that card/monitor uses. You've got one heck of a cad/cam workstation, but it's not ideal for gaming. Mostly because multi-display gaming has very strict limitations that would require you to change the way you have your machine connected to the displays. Generally speaking, there is no ideal setup for 3x1920x1200 surround gaming at the moment because SoftTH is just a bandaid hack to get things to work and Matrox doesn't yet make a box to triple span that display resolution.
Options:
1)
3x1920x1200 = SoftTH + 2 video cards. 2 displays on main card, 1 dispaly on secondary card.
Will work with some DirectX games after manually configuring.
2)
2x1920x1200 = XP + 1 video card with 2 displays connected + horizontal-span mode. (note TWO displays)
Will work with almost all games.
BTW: I really wish I had your machine as a Catia workstation at work. I'd kill to be able to do my work on that. :D