Short of a splitter or receiver, something's gotta give. Ditch the Apple TV & get the cheapest mini plugged direct to tv via HDMI (or TB for 4K) & use infuse/plex on the mini with the audio out to your DAC that way.
If you're fixated on the Apple TV, ditch the speakers in favour of something like the KEF LSX II that have airplay & network capabilities -
https://uk.kef.com/products/ls50-wireless-2
Or have both with the mini dedicated to film duty & your uber expensive speakers & the apple tv routing to KEFs or similar.
Or get a 2nd hand 3rd gen Apple TV HD that had optical out, but doesn't do 4K.