At the moment I'm unsure of whether the A16 can actually accept upstream-decoded Dolby Atmos 16-channel LPCM... if the Oppo 203 could even put it out via LPCM, which I don't think it can. So I expect that I'm still going to have to insert the A16 between the Oppo HDMI1-out and the AVR, and use BITSTREAM. So HDMI-in/out of the A16 had better work with my Yamaha AVR. And we'll see how HDMI-bypass works.
I don't know what I was thinking. I'm an idiot. The fog of war.
Just because The A16 only accepts 8-channel LPCM via HDMI doesn't mean I have to place A16 between Oppo and AVR in order to handle Dolby Atmos. The A16 accepts 16-channel bitstream via HDMI, and it also accepts 8-channel bitstream via HDMI. And the Oppo can deliver HDMI audio output as either LPCM or bitstream. As it happens I currently have my Oppo set to deliver LPCM because (a) I have an A8 which requires LPCM, and (b) 8-channel LPCM is no problem with the 8-channel A8. Replacing the A8 with an A16 simply means that I can now feed bitstream for ANY codec and for ANY NUMBER OF CHANNELS from the Oppo rather than LPCM, since the A16 can now do the decoding rather than requiring the Oppo to decode as was the case with the A8.
So that means I clearly can still operate the Oppo in "split A/V" mode as I do now (i.e. with no HDMI pass-through), with HDMI1-out going video-only to my AVR and HDMI2-out going audio-only (but now bitstream instead of LPCM as it used to be) to the A16.
In other words I do NOT have to daisy-chain things as I earlier mistakenly said I would have to, with A16 placed between Oppo and AVR where it would pass-through HDMI to its output and on to the AVR. I can simply leave things cabled exactly as I do today, with Oppo's HDMI2-out audio-only now set to bitstream and going to the A16 and no further. No need to pass-through HDMI out of the A16. The only change is to set the Oppo to now deliver bitstream out of HDMI2 instead of LPCM. That means I can in fact deliver all audio codec sources and either 8-channel or 16-channel via the Oppo's HDMI2-out, since it will now be the A16 doing all the decoding no matter what the source.
I do NOT have to place the A16 between Oppo and AVR in order to handle Dolby Atmos. I just need to change the Oppo to put audio out over HDMI2 as bitstream feeding the A16.