You can’t add more to the Home Theater, except the extra Sub.  The full room setup is a soundbar, 2 surrounds, and 2 Subs (1 if it is a Sub-Mini).

Sorry, I’m not up on the package deals. What’s in the Sonos Ultimate?

Based on my guess of the title, it already has a pair of Era 300s, you can not add any more speakers to a home theater room. The maximum is a Sonos Arc, two Sonos Subs, and two surround speakers (of matching type). 

You could certainly get extra speakers and set them up as another room, both rooms would be in sync when streaming music. However, when streaming the TV’s input, there would be a slight delay of at least 75ms between the two Sonos ‘rooms’. 

Thank you so much for the responses. I was unaware you could Not add anymore, I havnt not heard the set up yet as it has not arrived, but I am assuming I will not be disappointed. I am definitely going to add another Gen 3 sub. I owned a klipsch black label set up about 10 years ago, so that is all I know. So taking this leap to Sonos as my home theatre set up with my Hisene” 120” short throw laser projector should be optimized, I am hoping!