Pretty straightforward:

Arc Ultra plugged into the TV. 

Then position and add the Era 100s as surrounds, through the correct process in the app.

Then position and add the Sub mini as the sub, again through the correct process in the app.

No amp needed. 

Thank you.. is there anything I can use the amp for that would tie in directly to my tv still?

I also have a pair of Polk passive speakers not being used at the moment. 

Just trying to decide if can add value with the amp in use at all or just return it. 

Not with the TV, your Sonos ‘room’ for that already has the maximum number of speakers.

If I were you, I would set up the Amp as a separate ‘room’ in the Sonos software, and put those Polks to either side of the TV, and use them for music streaming. But of course, they could go in any room, not just the TV room. 

Can Alexa stream music through the amp into the Polk passive speakers?

Complex question.

Alexa can be told to stream music from Sonos on the Amp (controlling the Amp via voice control, with the Amp using the Sonos connection to music). 

Or, if your Alexa device has a line out, you could get the appropriate cable and hook your Alexa device to the line in on the Amp, and use the Alexa generated music to get driven by the Amp.