This would work fine. I’m a bit anal with respect to network wiring and I recommend having a network connection available for all wire capable units in the room -- and a capability for adding more connections for future additions.

As @buzz said the setup will work as you desire. Also know that in ceiling speakers used for surround are going to limit furniture arrangement to ensure the proper listening position for surround sound. 

In addition any music streamed to the setup will be played through the Arc as well. You can set the in ceiling speakers via the Sonos App to play music as Full or Ambient. Surround speakers in any Sonos setup cannot be targeted separately as they are part of the main speaker which in this case is the Arc.

Below is another option; albeit more expensive:

For maximum flexibility you could use Sonos One SL’s on stands positioned  as surrounds. This would allow a bit more freedom for furniture placement as long as the seating isn’t to far off axis for the surround effect. You could still install the in-ceiling speakers (with Sonos Amp) in the center of the room as Music only speakers. 

Thanks!

would this also work with beam gen2? 

Yes. However, the Beam is a smaller speaker with no upward firing speakers. Therefore the dynamics associated with Dolby Atmos material would not be as engrossing as with the Arc. Dolby Digital 5.1 would be great assuming the room size is small to medium (i.e. large Bedroom). Although, I have an Arc in my bedroom. A little overkill; but I like overkill

This is great! Thanks for your advice on this people!

Oh… to wire this up…

Arc to tv via HDMI, ceiling speakers to amp, amp to tv, sub is wireless?

does the set up know how to play through every speaker even if they’re all wired up to different inputs?

thanks again!

What different inputs? To what speakers? The Arc (or Beam) gets it’s input from the TV and will relay that via a dedicated 5Ghz wireless connection to the Sub and the Amp. The Amp has a wired connection to it’s speakers.

@Johnosono

Setting up a home theater is as follows:

Make sure you have good WiFi. If using a WiFi Mesh setup you may want to consider connecting a Sonos Boost module to your main router via Ethernet. Doing so will prevent Sonos from connecting to the wrong node in a Mesh setup. Mesh networks or those with range extenders/access points can be problematic for Sonos. 

Download the Sonos app to your iPhone or Android phone 

Register with your email and setup a password 

After the initial registration all you’ll have to do is launch the Sonos App from your device. No need to enter a password.

Plug in all your components to electrical *

Setup the Arc first

After the Arc is online you’ll be asked if you’d like to add a sub and/or surrounds (ie Sonos Amp with in-ceiling speakers)

Note: The only speaker that connects to your TV is the Arc via HDMI to the ARC or eARC port on your TV. The same applies to the Beam Gen1 and Gen2. On the off chance that your TV does not have HDMI the Arc can still be connected via Optical using the enclosed HDMI to Optical adapter in the box. If none of the inputs are available on your TV we’ll have to assume you’ve been under the perverial Rock for the last 20 years.

After everything is set and online; if using an iPhone, you’ll be given the opportunity to use Trueplay to balance the sound to the room. 
 

 * Click the link on how to use the Sonos Amp to drive surround speakers. 

https://support.sonos.com/s/article/4717?language=en_US

Thanks for this AJTrek1. Appreciate it!