I don't think you have tried the solution that I proposed in my post.
I bought a Roku 3 to be my guest bedroom Netflix streaming device. It worked great, too great in fact since we gave it to my wife's cousin cause she liked it so much. The Roku is my go-to recommendation when people ask me what streaming box to buy. I love me some Roku.
I am also familiar with Media Browser 3, and I have had a Plex server since 2008. They are all very nice programs and great solutions for streaming media to a variety of clients.
But the Roku's GUI is nowhere near the fanart magic of Aeon Nox, nor can any of those library manager programs provide on a Roku what XBMC can provide on a HTPC.
With XBMC if I want I can get really detailed information on the fly. I can pull up a sub-menu that will list for me the actors in each of my 1600 movies and it will generate that list onscreen after only a short pause (and we are talking tens of thousands of actors). Or every movie by year in seconds.
And there are hundreds of plugins that you can extend XBMC with. Some like auto skipbacks after pauses and tvtunes really add to the experience.
I will admit it was a pain to setup XBMC for my library- the default MySQL settings choked on that many movies. But that is the advantage of the HTPC route- you can throw more hardware at it. I threw in more ram, tweaked the MySQL config and now its faster than ever before.
I can't throw a better GPU in a Roku and make it look like Aeon. And it is a pain to import a library like mine into MB3 or Plex. It takes a very long time even on a quad core desktop.
A Roku is the best solution for streaming period and a great solution for local playback. But if you have a large library and some spare time XBMC on a HTPC can be the best local playback experience possible.