Options for multi-room audio?

[Kryptik]

Aftrnoon all. My first post in this forum. I think there may well be people in this forum with a wealth of experience greater than my own, but I hope I can contribute something of value on this topic.

I've recently acquired a Google Chromecast Audio and been impressed to such an extent that I now have a handful of them for the purpose of synchronised multiroom use. I've found the implementation simplicity personified and the experience seamless.

I use Minimserver on the PC (obviously), BubbleUPnP as a control point and wirelessly connect to a single, or 'grouped' multiple Chromecast Audios. The initial setup of the CCA (Chromecast Audio) is done using the Chromecast app, as is the grouping of them if using more than one. Consequently this is restricted to Android users only.

In my main listening room I have the CCA connected via TOSlink (to mini-TOSlink) to a DAC.
The TOSlink limit of 24/96 restricts the quality of passthrough possible.
Using the optical connection bypasses the CCAs internal DAC allowing mine to do it's job.
In the living room I connect the CCA to my AV amp.
In the kitchen it plugs into the aux connection of the radio using 3.5 mm mini headphone out.

In BubbleUPnP they appear as individual renderers and the groups are displayed too as their own entries.
You can stream different music to each one, or the same stream to the group, all at once.

The CCA as a means to do just the network transport of data is fantastic and since the December firmware update that enabled multiroom I can't fault it at all.