Sonos doesn’t make ceiling speakers. They are Sonance speakers? Either way, you can use amp equipment with them, they are not limited to Sonos. To answer your question though, a single amp covers the 2 front speakers with a phantom center channel. Phantom, as in there isn’t actually a center speaker used. None of the Sonos products could be used to power your existing center speaker. A second Amp would be used for the two rear surround speakers.
If I had these existing speakers, I would do one of three options. A - ignore them, as ceiling speakers are not good for home theatre. B - Use a different brand receiver to power the speakers. Get a Sonos port to connect it to a Sonos system if you wish. C- Use the ceiling speakers, but only for music. Get a single amp connected to 4 of the 5 speakers, and then get a Sonos Arc, Ones, and Sub for TV audio.
