Apart from Sonos in general being awful[1][2], their web site seems to be pretty bad, too. Not only is there a modal "subscribe to our newsletter" box in that link, there's also a separate modal cookie warning which blocks the modal newsletter box. It's like frustrating users is core to their mission.
I had a houseful of overpriced speakers, some only 3 years old when they decided they were too old to support in their rewritten app, or some lazy crap like that.
For GP; I use some cheapo (sub $50) "100W mini amps" from Amazon. They seem fine to me.
Sonos makes this specifically. Has an RCA and HDMI input, along with being a Sonos device for streaming audio.
The only downside is the price.