Main idea with WiFi, Ethernet or async USB is to strip timing from the music and send it as data, to recreate timing again on the other side, far from the computer. Computer quality, playback program etc. become irrelevant (cheaper that way), while computer’s electrical noise is further away. Recreated timing has to be perfectly steady with no jitter - otherwise music becomes "noisy". AirPort Express is decent on Toslink output but it still produces some jitter that is suppressed by Benchmark DAC1. It can also be done with reclocker.
I’m not sure what would be the best in your situation. You can go with async USB, but that requires async USB DAC, or replace AppleTV with something better. Squeezbox was decent, but no longer available. There are Sonos wireless bridges, but I don’t have experience with them.