The X850 can not be flashed. The x800 can but with VGA only, DVI does not work . The 6800 gt Has Working DVI , BUt that card will not work in a MDD. Your best bet would be eather the 7800 gt if you can get someone on Strange Dogs to flash it (the rom is not public). or the 9800 pro.
_________________________
Mac Pro
Powermac G5
Powermac G4 DA
Sawtooth G4 AGP
Powermac Cube
Atari 2600,