If you are running the S2 app, you could group the Era 300s with the Playbar setup, but you will likely experience a slight audio delay from the Era 300s when playing TV audio. Streaming music will be in sync though.

There’ll be a 70 msec delay in the sound from the Eras (or any other speakers/rooms grouped to the tv source) so it’ll probably sound muddled. 

I’m not sure just adding speakers would improve the sound. And the term “improve” could mean something else to me than it does to you. What do you want to achieve?

I was thinking more of enhancing, adding more to the surroundsound effect even if the Era 300s would not be part of the surround sound configuration, I guess was more of what I meant. Also I was thinking about removing my Sub and adding it to the new Livingroom1 when streaming music. I kind of changed my mind when nik966a said there would be a 70ms delay with my suggested setup when playing TV audio, since I use my speakers more for TV audio than music.

It will actually do the opposite.  Any grouped speaker is not only going to be delayed by at least 70 ms, it is going to be playing a stereo downmix of all the other channels.  This means the front L/C/R, and the surround L/R are all going to be playing out of the grouped 300’s.  

So any front sound stage, and any surround effects are compromised.  Any dialog or action tied to the screen will also come from the sides.  Any directional effects in the surrounds will sound like they are scattered throughout the room.  And all will be delayed on top of that mess.