Video Card Questions - Mac

Hey guys,

[Originally posted in C6 forum, told to move it here]

I’m using Cubase with 3 monitors on a macpro 2x2.66 GHz 6core. The Video card right now is the standard ATI Radeon HD 5770. I would like to add a flat panel 50-60 inch to the setup to mirror the cubase video window. What cards would y’all suggest for this task…and just as importantly, are there any software adjustments I need to make within cubase to allow for this.