I just wanted to update this. Thanks for all the information provided here.
I was able to get with my dealer and was able contact Kenwood directly. After getting through about 4 people we got someone who actually knew what we were talking about. Kenwood said that the KMC-35 & 36 are the only officially supported microphones for these radios. When asked about the dual mic issue and the advertisement of this feature for the mobile radios, they basically dodged the question but said something to the effect that mobiles generally do not need the "enhanced" noise reducing that the portable radios generally require.
I asked about if they are going to produce a dual mic version for the mobiles but didn't get a real answer. Which they may not need an "enhanced" mic, but I'm not too happy with them right now, I have almost a hundred nx800's in service for possible upgrade and 750$ for each 5800, and I'd expect correct, easy to find information.