3D Enabled on dual video card setup

I have a NVIDIA Geforce MX 400 and a ATI All in Wonder Pro in the same system. I am using XFree86 setup to have the NVIDIA on one screen and the ATI on another. When I try to setup 3D in SAX2 it says it is unable to with a dual monitor setup. Is there anyway to get around this? Would it be possible to have two different xf86config files and switch between the two when I want to play games? Or, come to think of it setup different runlevels to run XFree86 in 3D enabled mode for one setup and XFree86 in TV enabled mode for the other setup? NeoFax