I've been testing module 8 with a macbook pro 256Mb Nvidia (shared memory). I'm also able to get 3 video projectors connected to the MatroxTriplehead2Go with a 800x600 resolution (for each projector that give a total of 2400x600 resolution). You need to check matrox website to see wich best card gives you the best resolution. If you are going to use mac pro then you can use several cards (4 max) to get 8 outputs max.
Related to projectors, there isnt any projector that when goes black, stop emmiting light. I'm using Barco R12+ performers, Barco IQ300 (old old old) and Nec NP4000. Only the barco projectors give me the hability to black out the output, but for that i need to press PAUSE in the remote controller. This pause is a shutter that closes behind the lens and stop emmiting light. But even when they go black there is always some light going out.
Hope it helps