Just an FYI: Some interesting stuff on prepocessors from when as I was looking last year
First, and I'm not 100% sure about this, I kind of remember reading that a bunch of the 16 channel prepros cheated a bit on the wide channels for ATMOS. Instead of placing object using the ATMOS algorithm they derived it by matrixing the fronts and sides together. Might have been resolved by now as it had to do with something Dolby needed to support.
The 2nd thing you might what to look at is some processors include the subs out in the 16 channel count (like the RMC-1). Some like the prepros like AV8805 claim 13 channels + 2 subs so you could say it's a 15 channel processor.
Also the 8805 does a trick to support all channels on Aura 3d ... it provides 2 extra output which can drive two more speakers. When Aura 3d is in use it steals two channels and sends the VOG and center height info to the extra channels.
