What means there exists to have three monitors, all controlled by Xmonad and have hardware 3D acceleration as well?

I had the pleasure of using three monitors earlier this year, and while Xmonad and Xinerama handle three monitors easily, I had to throw in an extra display driver, and also let go of Nvidia's own TwinView (which is a hack on Xinerama). This left me with no HW acceleration and some flickering as double buffering wouldn't work with certain applications. However, the three monitors handle so beautifully that I had hard time coming back to two.

I understand the easiest way to achieve HW-accelerated tri-head combo is to split into two Xorgs. I wouldn't be able to switch windows between the Xorgs, so I'm not really into this solution.

What's more, having a cheap and old PCI card along with even slightly better PCIe seemed to slow things down. Even if I occasionally disabled the third monitor from Xorg configure, I couldn't get HW acceleration to work. Only after I physically disconnected the old PCI card, I could get the games back in business.

Would a Matrox Dual/Tri-head2go and a powerful Nvidia GPU do the trick? I understand Xmonad can be configured to "believe" that a "single" (as Dualhead2Go will merge) 3360x1050 display is actually two different ones? So that Xmonad's Mod-w and Mod-e would work properly there.