1. A Sonos Play speaker is independent of a amp or receiver based system. You would use a Sonos Connect for that.
2. In an AV system you would want a high quality surround sound receiver such as Marantz or Anthem. Other options might be Onkyo or Sony. Some Sony receivers are designed to integrate with a Sonos Connect directly so that might be good if you are using Sonos for distributed audio.
3. If you are doing a distributed audio system (no home theater) then you could use a bunch of Sonos ConnectAmps. Each will power up to 4 speakers. You would want one for each area. You could also use a multichannel amp with a number of Sonos Connects. This allows for higher power in some zones. There are many amps like this so it would depend on...