You can only add two surround speakers in a Sonos home theater setup.

You cannot ‘bond’ further speakers to the Sonos Home Theatre that you’ve mentioned, other than Sonos Sub(s)**, you can only ‘group’ the other Sonos speakers/rooms, which is fine for music playback.

Note however, that TV audio sent to ‘grouped’ rooms has an approx. 75ms (minimum) delay due to audio buffering, to cope with the demands of TV audio over the local network.

There are tools in the App to adjust the TV and group audio-buffers, but that may lead to lip-sync issues with any video on the TV screen. See these hopefully helpful support links:

• https://support.sonos.com/en-us/article/tv-audio-and-video-are-out-of-sync (TV Dialog Sync)
• https://support.sonos.com/en-us/article/tv-audio-stops-or-skips (Group Audio Delay)

**Note: up-to 2 Sonos Subs (not a Sub-Mini) can be bonded to your Sonos Home Theatre (one must be a Gen3), or only one Sub-Mini can be bonded instead.

Thanks for that. I've already got the 2 bonded as Surrounds so will use my other 2 for music instead.