Actually Google Cast is still the name of protocol, but instead of calling partner hardware "Google Cast devices" in marketing, they'll be called "Chromecast built-in".
Google Cast = the underlying casting Protocol
Chromecast = A Google Cast device made by Google
Chromecast built-in = Any device which supports the Google Cast protocol which isn't explicitly a Chromecast
I have been looking for this answer as well. From what I have found the Sony and Vizio cast speakers seem to be the best bet. Also not sure if it matters to you but Sony seems to be the best if you want a portable, battery powered option.
A number of people discussing chromecast audio are only referring to the small add on device that makes other speaker systems work with casting. Be aware that google is licensing the technology and now a bunch of other companies are making devices with chromecast audio built in. Just quickly browsing, I saw sony speakers starting at $150 and B&O speakers that ranged up to $2849. They all work together and can be added to groups through the google home app.
If you get a google home device, you can even just say "Hey Google, play music on house" and if you had setup a group with all your cast devices, it would play throughout the house. No need to send it from your computer.
This page has more info - https://www.google.com/cast/audio/
Your TV is basically running the same OS as a Chromecast. You cannot browse for anything on your TV from your couch. The TV simply waits for a URL to be sent to it and it will fetch the video stream.
A mobile device would be best, a laptop would also be an option. If your only way to browse for content is from a PC that's not in the same room as your TV, then it's going to be a bit cumbersome. I would recommend finding another TV altogether (preferably one that excels at being a TV, meaning great picture quality) and adding a box to it that has the input options you're looking for (handheld physical/tactile remote, with additional features like voice search or private listening).
> bunch of powered speakers and a bunch of Google's Chromecast Audio plugs
There are actually speakers with Google Cast built in now. List here.
The Chromecast Audio itself does support multi-room audio. I assume the speakers with built-in Cast functionality do as well, but technically they are a different product so it would be smart to double-check.
Really? You need a Wikipedia article just to validate that something is real?
Okay, well then go to your Chromecast link and scroll down to the part that says GOOGLE CAST, you idiot.
And since you're as dense as a fucking diamond, there's this website called "google.com" that let's you search for things on the internet. If you search for "Google Cast" then magically this URL appears:
Yes, Google Cast can be found by googling!!! It's a miracle!!!!!!
And if you want to talk Google Cast then go to /r/GoogleCast.
Oh wait, I forgot you're too stupid to find it.
My household is basically an Apple & Sony environment, except for one Roku. So AirPlay is easy enough for audio/video.
You might be interested with Google Cast for Audio since you already have Chromecast. Oh, and here Chromecast audio