AMP 3.1 setup with passive speaker.

Thanks for the reply.

Not even using two Sonos AMP’s?

Not even using four Sonos Amps.

Well actually, @Airgetlam & @Lukestar, You can set up a Sonos Amp as center/left/right + subwoofer and bond a second Sonos Amp as rear left/right surround.

In this configuration, the center channel is a phantom effect created by sound engineering magic and It would not be able to drive a separate center channel speaker. The third party sub-woofer would need to be wired to the primary amp not the one configured for surround.

I apologize for the extreme lateness of this response but I hope it helps!

Right. Because the center channel is a ‘phantom’ channel, it’s a bit disingenuous to claim it a a center speaker, most people expect that if you say center without the mention of ‘phantom’, you’re suggesting there is a connection for a third ‘center’ speaker on the Amp. Which there isn’t. 

The OP said they were attempting to set up a 3.1 system with his Paradigm speakers. Sonos doesn’t support setting up 3 speakers in the front. Just two, with the addition of the ‘phantom’ channel, which leaves the OP’s Paradigm speaker for the center unconnected. 

You are correct in that, @Airgetlam.  This setup solution assumes that one is ok with leaving a perfectly good center speaker out of the mix.

Your mileage may vary, in this case.  

What you need to integrate that setup in the Sonos ecosystem is any 3rd party receiver of your choice and the Sonos Port. 
 

If you don’t already have a receiver, make sure to thatthe receiver you get, is able to detect signal from it’s line-in so it will turn on and switch to the right channel when you stream something to the Sonos-amp. 
 

There are several receivers labeled “Works with Sonos” which are ensured will work as described. 
 

Note that the Port significantly cheaper than the AMP so you should be able to get both a receiver and the Port without spending much more than on the AMP (can define be done for less than the price of two AMPs).