I had some luck with this card and Graphics Enabler, but truthfully never got it to work acceptably. (I'm using 10.6.2)

I dumped my own BIOS using NiBiTor

ran NVCAP on that to get the needed string

OSx86Tools - Created an EFI string using custom generic 512 setting with the nvcap from above

Removed Graphics Enabler from the com.apple.Boot.plist completely

Added to EFI string created in OSx86Tools myself into my Boot.plist

Booted up and card works great.

*note I tried using BIOS files online first for this card with varied levels of success, I don't recommend it.