I know 3dfx made an announcement a while back that they were going to add ADC connectors to their future products, which I took to mean not their current Voodoo 5 & 4 products. Probably Voodoo 6 or whatever. A long time from now. The Apple Store is selling an ADC->DVI adapter, which may or may not be what you need (I can't remember which way it goes: DVI connection to an ADC port or an ADC connection to a DVI port, probably the latter).
Dave Corder