So, as far as I can tell, from the lit of research I have just done, It is hard to tell if all these devices speak the same language. The Lightronics
dimmer pack can speak NSI multiplex, but I am not sure if this is the same as NSI Microplex. My biggest concern about connecting the two different dimmer packs together is that NSI Microplex supplies a "phantom power" voltage so that the NSI controllers don't need to be plugged into the wall, but I don't know if that is compatible with the other components you have.
The only information I could find on the MC8C was in Japanese, so that is no help (unless you speak Japanese). I would have to imagine that if all of this gear was purchased together it would all work together, but you never know (well, someone might).
Here are some links for you though:
NSI manual
Lightronics Info