A Sonos amp can be used to power 2 pair (4 speakers) of 8 ohm passive speakers, which is probably what your ceiling speakers are.  You can also use 3rd party impedance matching speaker selectors, which would allow you to connect many more speakers to a single amp, but you will be splitting the ‘power’ amongst more speakers and they won’t get as loud.  You can set the Sonos amp to play mono instead of stereo.

You can also get a Sonos port, and connect it to a 3rd party amp/receiver to power your ceiling speakers.

You have lots of options really.  The best solution depends on budget and what you’re hoping to achieve.

I’d get a Sonos Port and a multi-channel external amplifier to power your speakers.

The Port would source the sound and provide the basics like volume and tone controls.

The external amp might provide individual speaker level controls or you might need external volume controls to equalize the speakers volume to match your space.

I’d run the speakers in Mono mode as a first choice, unless they are dual voice coil units that provide full stereo sound from each speaker. That difference in speakers also impacts how many channels of amplifier you need.

You can alternate L/R such that a listener will always tend to be positioned between a Left and Right speaker.  There will not be a global sense of “left” and “right” in the room, but each listener will have a more special experience.