Grasshopper-
You certainly have a very capable system and upgrading the MacMini should prove to be a wise decision. There are plenty of choices and we all have our favorites.
Personally, I have been happy with the Bryston BDP3. It can be ordered with built in WiFi or simply plug in its Ethernet directly into your router or a WiFi extender if hard wiring would involve breaking down walls.
You can add your own SSD for local storage and it's compatible with Qobuz and Tidal. Its Manic Moose software is very stable and great sounding. Bryston has been working on a major revision to the Moose that will be more modern in its GUI and interact with other streaming services. It includes a 60 day ROON trial although I felt the ROON sound quality was lacking compared to Manic Moose.
Enjoy the Hunt!
John