Generally-speaking, you ideally want to match your front three speakers - either three of the same make and model, or L+R and a matching CC from the same series. (Version matching is sometimes also important.) Matching your surrounds isn't as important, but if the matching surrounds are well-rated and within your price range, there's no reason not to get them.
That said, I used to own a pair of Monitor 7v4s and a CC-370v3, and I found that the 370 sounded just a touch "thin" compared to the M7v4s. (My understanding is that the CC-350 and the CC-370v1/2 were better matches than the CC-370v3/4 to the M7v3/4s.) I experimented with a couple of different CC speakers and was surprised to find that the Studio/CC v2 paired up really nicely with the M7v4s.