I finally received a $25 widget that accepts eARC and outputs HDMI, so I was able to compare the sound using the TV speakers and using my audio setup. The two sound a bit different, and I'm not sure which I prefer. It’s not worth powering up the Ayre preamp, amp, and Bryston processor. The Ayre DX-5 DSD sends superb video to the full-array TV -- I was perhaps unreasonably leery about OLED.
Sony TV sound
Since I installed an 85" Sony TV with eARC last week I've tried several widgets aimed at connecting it to a Bryston SP3 processor that predates ARC. I assumed the surprisingly good sound from the Sony would be fine for TV, but not for movies. Last night I discovered how wrong I was. I played a version of Legend of the Ring and was astonished by the sound: immersive with a large frequency range. How Sony achieves that is beyond my understanding, but my quest for connecting my audio setup with the TV is over. The Ayre gear will be reserved for DSD and Blue Ray, except the Ayre DX-5 DSD sends superb video to the full LED array TV. I'm a very happy camper.