B W CDM 9NT's with B W HTM2 center

It should be fine, especially if you consider upgrading to the Nautilus range in the future. The CDMCNT matches the CDM1/CDM7 better than the CDM9 while the HTM2 fits the N805 and N804 better. The CDM9NT is just sort of in the middle. The HTM2 is a better sounding unit than the CDMCNT, with the voices sounding more natural so why not use it?

Blackie's advice appears to be sound and the fact that the CDM 9NT uses the same drivers as the N804 would make a strong case for using the HTM2.