I just bought an apple 23" cinema display and plan on buying the matrox mxo. I was gonna use my sony pvm crt monitor to grade my color and what not. It seems like the matrox mxo would make my apple monitor be just as good at grading color however. I plan to edit hdv mostly but still output projects usually to ntsc 720 by 480. So with my doing my final outputs in SD but editing using native 1080i should I keep the pvm or just color grade on my apple and have my timeline on my other computer screen?

I do CCing on a Sony PVM as well. I edit both DV and HDV with no problems.

I do CCing on a Sony PVM as well. I edit both DV and HDV with no problems.
You are still able to run 2 computer monitors and a pvm with the matrox but one of the 2 computer monitors would need to be connected into the internal video card right ( mine has two dvi outputs and the matrox seems to have just one out)