I am typing this now on a 1st Gen Quad running a 285GTX. HOWEVER....this is using Netkas' fine Injector package........AND............currently it appears that a "backup" Nvidia card needs to be in the machine with a working EFI ROM. This has been tested with an 8800GT and a quasi-Quadro 4500, both running an EFI-32 ROM.
In theory we should soon have confirmation that a 7300GT works as well, this will allow for no power splitters needed.
I have every reason to believe that Netkas will hit upon what is needed with injector to obviate need for another Nvidia GPU. So perhaps soon it will be possible to have this work with JUST a PC GTX285.
I have both DVI ports working and both have worked with 30" display and a 2407 on other DVI.