Been running a Quadro4 900 XGL for a few days now. Works great - wish it was mine.
The card is from Dell and is essentially a GF4 4600 Ti tuned for accuracy instead of fps.
So on a ECS K7S5A the following cards works for me:
Leadtek WinFast GeForce2 MX DH Pro
Dell Quadro2 MXR
Dell Quadro4 900 XGL
This one does not:
Gainward GeForce4 Ultra/650 (4200 Ti)