Glad you found David’s project info. It was the Allo DigiOne HAT (SPDIF output for Raspberry Pi) that got me started on this road. For $125 plus the cost of the Pi running a free OS such as DietPi, it can be amazingly competitive sonically with a 218 if given great power. https://allo.com/sparky/digione.html

Should you progress to Audiolinux and Diretta, David has written a driver for HATs like this.

If the MS600 has Comms out, you could leave it connected to the BNC on your speakers for control while music flows from the Pi.

Server: Audiolinux Roon NUC w/HAF room correction and crosstalk cancellation
Theater: 218, Allo Signature, miniDSP, HD621, C61R, DSP5200SEu, 420, 33, NHT subs
EtherREGEN w/Finisar fiber, Shunyata Denali
Living Room: RPi4 Diretta Host & Target, Ghent USB > Singxer SU-6 > AES NA M-Links > DSP9
Shunyata TritonV3, LHY lps, Farad Super3, Stack AUVA feet