Hi, and thanks for your question. Yes! If those in-ceiling speakers are powered by the Sonos Amp, you can use those as surround sounds with the Sonos Arc.

Hi, and thanks for your question. It is possible that this could severely decrease your sound quality, as the front speakers are pointed straight forward, and the atmos speakers are pointed up. However, every room environment is different so it's difficult to say how much it will impact your experience.

Hi, and thanks for your question! Depending on the impedance of the speakers you can run 2 pairs of speakers on one Amp. Keeping in mind that any speakers that are plugged into the same Amp would always play the same thing at the same time. Another option would be to buy a multi-channel amplifier from another company and use the Sonos Port by plugging it into the amplifier. This would be a good option if you want all of these players playing the same thing, at the same time. If you'd like to have more control over which rooms are playing, when, and at what volume they're playing then multiple Sonos Amps would be the best solution for you.

Hi, and thank you for your question! The first thing to we'd like to mention here is to make sure that you run our Trueplay tuning feature with an IOS device. (Has to be IOS because of the consistency with the microphones) This will ensure you're getting the most accurate sound for your space and could make a big difference! If you have done that or are not able to, and still not getting enough sound in the back of the room, then yes, this speaker will fill a large space nicely. To clarify, this speaker alone can be grouped to play the same thing your TV is playing in the back of the room, or two of them can be used as wireless surround sounds.