Your right about the 32-bit part but I dont think the FX's support DX9c. Also the Fx are really slow when running in 32bit precision(look at far cry b4 patch 1.1)they usually have to fall back to lesser precision whereas the GF6 series run everything in 32bit without loosing performance.
Asus P4P800DX, P4C 2.6ghz@3.25ghz, 2X512 OCZ PC4000 3-4-4-8, Leadtek FX5900 w/ FX5950U bios@500/1000, 2X30gig Raid0