Can I add an ATI card to a Nvideo card Mac Pro

[RickR]

I have the Jan 8th Mac Pro and purchased it with the NVidea Geforce 8800 GT and want to add a 2nd graphics card. Will I have to add the same graphics card or can I add an ATI Radeon HD 2600? Will the two work okay in the same system using separate monitors?
What is suggested as a good 20 ft. DVI extension cable? This is the approximate length I need.

[Eidorian]

It's fine having an ATI and a NVIDIA graphics card in one computer. The maximum DVI cable length is 4.5 meters at 1920 x 1200.