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,