yes the 4640 is the 2016 ultra, I'm not going to move to the 2017 or 2018 ultra, they removed optical audio out and cut the channel memory in half in those. which is ok if you don't have a lot of channels but I do. and no a micro SD is not a solution, the built in memory is much faster
OK, My needs are different, so I haven't noticed any of the issues others have reported, and personally I'm glad the optical port, and Dolby encoder is gone. In my setup it caused issues with the TV, and Roku trying to both do the same thing. Now The TV handles converting DD+ to standard DD, and I Have the TV's optical out connected to the sound bar so all connected devices pass through. Plus I have a Sony Android TV as my 4K display and it can pass all standard formats (DD, and DTS 5.1) through optical. If I want lossless audio I use the Sony X700 which has two HDMI outs, and then has the same Streaming Services I use on the Roku that can pass DD+. I mainly still hold onto Roku as a product for the unique channels other devices don't have, plus overall it's a good platform, though for other features I like, other products are better.
That's another reason the loss of the audio options on the Premiere+ doesn't personally bug me, I have the same feature in the sound receiver itself, and that's usually what I use. (if I use it at all)