for 9.2.4 to 9.2.6, I think would make some content with objects moving from from front heights to rears, and with content in all 4 heights in 9.2.4, to see if 9.2.4 was "good enough" before replacing an AVR (unless there is some other compelling reason to upgrade).
I could create the tests, if needed.
Re: Auro 3D Voice of God, yeah I didn't mention I have a 13th genelec in my "13.1"/7.2.4 setup in the studio, directly over head. Almost never used. If I had the Auro 3D enocder I would use it more.
On my Marantz AV7704 that forces a trade off between "stereo" subs and mono to both subs (which I doubt matters) with the VOG. Same for 16 line outs from the Realiser A16.