You're misunderstanding me, probably my fault so I'm sorry.
My current setup comprises of a Core 2 Duo CPU, a motherboard with an nForce chipset, 2 GeForce 9400 graphics cards driving 3 monitors. See "Conroe" in the link in my sig for the exact hardware. This all works absolutely perfectly.
Now I'm getting a bit restless and fancy updating the CPU, motherboard and if needed RAM. I need to know if a motherboard with Crossfire support will handle 2 nVidia graphics cards not in SLI. I might be being overcautious here, years ago I used AGP and PCI graphics cards together with out any problems. However, I haven't found any article/post where this setup is used.
If the hardware plugs together, is compatible and exposes the 2 graphics cards as 2 separate controllers to the kernel, then the software configuration is trivial, it's a case of booting a live cd, mounting my OS filesystems in a chroot environment and rebuilding the initrd so that the correct modules required to boot are present.