You don’t have to use the Sonos/Sonance ones BUT they are the only ones supporting six directly connected speakers. You could add impedance matching speaker controls if you want another brand.

I’m a fan of going at least one step up in wire size. Type depends a lot on where it runs, worst case look for direct burial and UV resistant with pure copper stranded conductors.

If you add a speaker selector (maybe one with impedance matching) you could choose which speakers play.

You have to get the TV sound into the Sonos system. HDMI to something or using the optical / RCA line out on the TV to something. You could then group that to your Amp but there would be a 75 MS delay in the sound.

My builders are asking that I purchase all of the necessary materials. Can you give recommendations on suggested products to get? Planning mounted Sonos/Sonhance x6 each traveling approximately 20 feet to an outdoor junctional box connected to the indoor Amp.

With respect to the TV interchangability - Is there a way to get the TV sound integrated into the Sonos Amp and back out to the speakers without delay in the sound? Seems like this should be an option for the price...

You probably should find a local installer as just what is needed for wiring varies by location and building codes.

I’d really lean to the Sonos Amp and six of the Sonos/Sonance outdoor speakers for the audio portion.