Well, I can only say that JRiver works! To be honest, I've not tried multiple audio tracks and subtitle tracks as I always strip them out after ripping and remuxing to get the "leanest" possible file, but I'm sure this all works. I use JRiver to stream via DLNA to a WDTV Live, using AVIs or MKVs, and the DD/DTS soundtrack is there.
I don't know about Mezzmo, but one huge advantage of JRiver over other media servers is the complete flexibility you have in defining your DLNA views and browsing structure. It will derive lots of metadata about movies and TV series automatically but you can also set up as many custom tags/items of data as you want and you can include any of them in your browsing menus, ordered and categorised however you want.
Note that you have a 30-day free trial of JRiver if you download it, so if your movies are already there and ripped than just point JRiver at your movies folder and import them. See what data it gleans automatically, see how else you might like to cagegorise your collectiuon, and set up your DLNA views.