Firstly, you cannot add the Amp to your 5.1 bonded HT setup without taking something out of the equation to begin with. Your setup is already a complete system for Home Theatre use.
The Amp together with some additionally purchased passive speakers, could be used to replace either the Beam or the rear Play:1 surrounds... but I’m not sure it’s really worth going to that expense, unless you are not happy with the current front or rear audio setup.
You could use the Amp elsewhere in your home (another Sonos room) if you wanted to, but again you will need passive speakers to do that.
If you were just thinking that adding the Amp to your existing system would somehow improve the sound you have already, I’m afraid that is not what the Amp will do.
If you’re unsure of what the Amp can do for you, then my advice would be to leave it at this moment in time.