I've been researching this all afternoon, and so far I've concluded that these are the options (for a six-zone system, for example):

1- High-end system from a company like Legrand, NuVo, Control4 (through an installer), etc. These are pricey and not user friendly.

2- Monoprice has a very inexpensive system here. 6 zones, supposedly good sound. But actually controlling anything you'd want to play seems annoying to me.

3- Sonos Connect:Amps for each zone. Very user friendly but super expensive. 6 zones would cost $3K.

4- Six Chromecast Audios plugged into six stereo amps. This looks ridiculous in my head, but in practice it should be one of the easier systems to use, and probably the cheapest. It would just look like crap in the closet.

The systems I keep coming across for options 1 or 2 all look so antiquated. They feel like they were designed to control little more than a CD player. I'm amazed that none of these systems have been brought into the 2010's with updated electronics. I could see something like that Monoprice unit being really impressive with the right software, and if I could control playback for streaming services from the wall controls.