ATI Radeon X800XT Mac Edition - hard to find since it's discontinued.
ATI Radeon X850XT OEM Mac card - hard to find because it's an OEM card.
Geforce 6800 Ultra or GT OEM Mac card - also hard to find since it's OEM.
By the way the ATI Radeon cards mentioned above offer only one dual-link DVI port whereas the Geforce cards offer two dual-link DVI ports.