And I hope to God you are not thinking stereo which is never to be done with ceiling speakers.
Dude, what exactly is YOUR expertise in this matter? I happen to be a Low-Voltage system designer, and I have a degree in the subject matter. I'm also a member of both CEDIA and InfoComm. We do it all the time in our industry which is exactly why MY industry isn't exactly fond of your trade trying to do OUR job. A lot/most of you guys just don't understand the science behind our trade.
This is the same reason why I constantly see homes built in sub-divisions with the homes Data/Telecom infrastructure ruined because some electrician who THOUGHT they knew what they were doing pulled the signal cable along side power cables causing so much crossover the signal attenuates before it can even reach anywhere in the system useful.
That's why stereo is never done with ceiling speakers or any other distributed system because you have to be smack in the center of two speakers on opposite channels and that doesn't happen with people all over a room.
Your definition of distributed audio is stunted. DA comes in two flavors constant voltage and low-impedance. What you seem to be familiar with is constant voltage aka 70v paging systems. You can in fact distribute audio in stereo. It's a lot more complex than wiring speakers in parallel, but if it wasn't possible I wouldn't have designed at least half a dozen home theaters for clients who wanted a small home theater in their living room with ALL in ceiling speakers such as the AIM series by Speakercraft.
Moving on from that, the way the user stated the question and given the information, it's not really an answerable question. MANY factors determine how speakers will be installed in a room for stereo, yes, STEREO sound in ceiling. Often you have to work with what the architecture will give you and even then the acoustics of the room can also have an effect such as in bathrooms. The intended listening purpose of the system also has a big effect of the system design, i.e. background music vs entertainment vs critical listening. Answering the question the original poster asked, an experienced professional would have asked for this sort of information.