Sonos AMP, ARC and 7.2 setup

Hmm, if i have to ditch the receiver looks like I have to run new HDMI cables behind wall to go from cable box, DVD player and AMP to go to the TV and separate HDMI cable from TV to Sonos Arc. need to get fishing I guess

Here is what I would do. 
 

Don’t get the Arc or the Amp. 
 

Get/keep a Pioneer receiver which works with Sonos. Could be the VSX-LX304. Typically priced at about the same as a Sonos Amp. 
 

Buy two Sonos Ports (or two used Sonos Connects second gen (with Play-buttons rather than Mute-buttons on the front). 
 

Buy the amount of third-party (or Sonance in-wall/in-ceiling) front and center speakers as you want plus one or two subs as you prefer. You could consider just using two floor standing speakers or bookshelves with updating speakers.

Now:

Connect the speakers in the living room to the Pioneer - leave two speaker-ports for the patio-speakers.

Use the Pioneer-receiver for HT. You will get 5.1, 5.2, 7.1 or 7.2 as you please. It will power up with your tv connected with HDMI and support any codec you like including Atmos, DTS and Dolby Digital Plus. The Pioneer has several HDMI inputs, so you can connect your Blu-ray player etc directly to that and only run a single HDMI-cable to the TVs HDMI Arc port. 
 

Connect the patio-speakers to the last speaker-ports on the Pioneer. It can run two zones. One will be the living room and one will be the patio. 

Connect the two Sonos Ports (or Connects) to the Pioneer and set up Works with Sonos. You can pair one with Zone A being the living room and one with Zone B being the patio.

Now, you will find both both Zones (the two Ports/Connects) in your Sonos app. If you stream to either, they will turn on the receiver and start playing. An update earlier this year even ensures that you can control volume via the Sonos app so they will work as any other Sonos speaker.
 

This sounds good. I wish I could have seen this in time. i decided to buy a Arc and AMP for now . I might buy a spekaer splitter to go between Amp ---(living room rear speakers and patio speaker). Decided not to buy front speakers for living room.  I already have a move and Play 5 so will keep building on the sonos system. Above soudns perfect however I am still not sure if we can connect 2 ports to drive a receiver like VSXlX304

Whether you can use 2 ports or not, I think you might be over complicating things a bit, at least in terms of control.  A slight modification to that plan, would be to use a Port with a Pioneer AVR that meets your home theatre needs, and use a Sonos Amp for outdoor speakers instead of a Port and the 2nd zone of your AVR.  The Amp is $200 more than a Port, but you won’t have to deal with trying to run a second zone off your AVR, and you likely will have more power to the speakers with the option of adding another pair if you wish.  You can also add a TV out there later on if you wish.

All of the new Pioneer Elites can run up to three zones using three Ports. Pretty smart for installers.  The main benefit is of course the cost difference between the Amp and the Port.
 

But you will of course be limiting the speaker ports - and draining power from the receiver if everything is playing at once. 
 

In the house we are currently building, I actually purchased a couple of used second gen. Connect:Amps for a couple of stereo speakers which are not connected to a TV. The second gen. Connect:Amps will be upgraded to S2 and only cost me a little more 200 USD a piece. Great value. 
 

In the living room, I will be getting a third party receiver from Onkyo or Pioneer and hooking up a single Port or Connect just for that one zone.