I don't know how well render setup has transfered from alpha to 1.6, but i can't see big errors in your setup or materials, except HDRI map in enviroment, which has very wrong mapping coordinates and that probably contributed to the noise greatly. Please see attached screenshot for correct coordinates setup. Keep in mind that you can change at will only U offset. Also you can set U tiling to 1 or -1, but not any other value, otherwise lighting will be incorrect.
I also added portals to all openings, but that is not strictly necessary and you can get noise free results without using portals as well.