We have DieHard report about the ASUS V8460 ULTRA succesfully  flashed with the PC GeForce 4 Ti4600 (Arti) 1105  ROM,

... and my (MacTron) failed with the Quadro 900:

http://macos9lives.com/smforum/index.php?topic=681.msg11447#msg11447

... but we are still in on track for Dual DVI nVidia 4600 cards. There are a few from MSI and Grainward, but may be those are really Geforce4 Ti 4800:  the AGP8X version of the Geforce4 Ti whith the GPU NV28. Here we have to be carefull, as the AGP8X cards need hardware modifications and the NV28 may be not compatible with Mac Os 9 nVidia drivers