Hi @Jumakisa,
As you’re searching for the right endpoint, I did want to mention one other thing regarding your post here:
You should be aware that we suggest customers to not use Apple Networking Gear, as we have often seen issues surrounding such equipment, enough issues that we explicitly mention staying away from Apple gear in our Networking Best Practices Guide.
You may also want to upgrade the router (before even getting the new endpoints purchased). While we can’t comment on a specific router model to use, generally speaking ASUS, TP-Link, Netgear routers have had the least amount of complaints on this forum.
If you want to start of small, you could try using a Roon Bridge device first and see how you get on with the current setup, a Rasberry Pi based Roon Bridge would be the cheapest option (setting up DietPi/Ropieee might require some time on your end though).