Hi, which multi room audio system (ideally with microphone to give vocal commands), integrates itself the best inside Home Assistant ? (I am not using Apple, Alexa)
a/ Sonos
b/ Google Audio Nest
c/ Bose
d/ Bowers & Wilkins
e/ Sony
f/ Denon
g/ or DIY with raspberry or anything else
It’s difficult to compare, as most of us would have only one at home, if at all… 
From above i would choose Denon, just because I have that, and it works.
I also have a Volumio network of players (straight and easy DIY), and that works fine too. The good thing about it is, it can make almost any amplifier/speaker join multiroom, as long, as there is a line in.
The “bad” thing - it is not free, multiroom is available for a small fee. But I found that worth the money
And based on my personal experience, I’d choose anything BUT Denon on that list and for a very specific reason.
Don’t get me wrong they make fantastic sounding gear… And if that’s your only factor it sounds good. I originally went with Heos equipment in my master suite as I had Denon gear in my rack and upgraded to a 4k capable AVR during my last upgrade cycle but… Im an Alexa / Spotify user and learned during the installation that, that particular combo doesn’t play well together under Alexa voice (my wife’s preference). The Alexa support for Spotify when using the Denon Heos skill is nonexistent - you can’t voice target the heos speaker if you use Spotify as the source. Apparently it’s a Denon thing to fix. It has been promised for enough years now it’s an empty one.
Is that HAs problem? No. Frankly. But for me at least, the total fail supporting Spotify on Alexa makes it a do not buy. (not going to change my spouse’s behavior, and it would ha e been a veto point had I known on the original purchase) It’s just as easy for me to go Sonos for the solution instead. I’ve stopped buying Heos one and gone to Sonos instead.
Edit: yes if they ever fix that issue it immediately moves them back to #1 for me.
What is mainly limiting in the free edition of Volumio ?
For me it will be the absence of multiroom sync and native support of Qobuz.
But it still is a very capable player.
I did get to it, when I was looking for software, which can take all of it out of my Rpi3 + HiRes DAC combo streaming Qobuz. It works, and it sounds excellent. There even is native HA integration.
For all differences see here:
The best is chromecast audios driving a multizone speaker and using Google hubs for voice control. In fact you don’t even need to use HA for media control - apps on phones can cast audio to the chromecast audios, and voice commands from the hubs support streaming services.
The chromecast audios aren’t made anymore, but you can generally find them on ebay etc… Works great and high family and wife acceptance.
Chromecast: 24 bit / 96 kHz max.
My Volumio setup: 32 bit / 384 kHz max.
I don’t need voice commands, my first demand is sound quality
That sounds like a neat product. I wish they had cast support, because that would allow folks to make a PC with a bunch of high quality DACs to drive multichannel amps - a DIY VSSL system.
I find my my chromecast audios quite good quality wise, though I use a different system for my AA receivers - the chromecasts drive speakers in the ceilings of a few rooms, so it’s not the highest quality speakers either.
Cast to Chromecast and Sonos is build in with the Premium version
No, I want the volumio software to be a chromecast target, not a source. I would like a higher fi version of a chromecast audio, esp if I could put a bunch of DAC’s on one PC and feed my amps from those sources. It’s not a neat install when you ahve 14 chromecast audio pucks velcro’d to a rack shelf. 
Not official, but it does exist…
Both of those involve volumio streaming to a chromecast device.
What I want is to have HA or any cast enabled app stream audio to a volumeio player using the cast protocol. And with aircast support in HA, that also would allow a volumio player to look like an airplay target as well.
Russound, VSSL, and a bunch of other players now support acting as a Cast target. But nothing DIY which is frustrating.
Hi,
Late answer but here is my actual setup with a DIY solution.
I use LMS (Logitech Media Server) as a server (on a NUC, but it could be installed in a raspberry or…), and then i connect every player/speaker as a client. On my side, i use different type of speakers: my PC, chromecast devices (google home, google nest, recognized in LMS directly), my AVR (Denon with a Raspberry PI with Max2Play, connected via RCA connector, as denon has not a chromecast built in solution).