Conference Room audio setup

My company is moving soon, and our new office will have two conference rooms; 12x13 and 18x13 feet. It's a drop-ceiling office.

I want to set up audio systems in these conference rooms, oriented at VOIP/teleconference use. My plan, so far, is in each room (one table) have two boundary microphones (A-T PRO44) on the table, going to an M-Audio M-Track 2x2, with outputs going to a Beringher EPQ304 (shared between rooms), driving ceiling speakers.

Then, to have a pre-recorded impulse response of the room in an echo-cancellation path on the computer.

What I have not yet decided on are what speakers, how many, and where to put them.

I suspect that ceiling speakers will have an advantage in echo cancellation because the audio path from speakers to microphones will be far-less affected by movement and number of people in the room, though there will be a disadvantage in the other end of a call being a bit disembodied in the room.

A pair of speakers on the wall near the projection screen would have psychoacoustic advantages in being a bit more point-source, making it a little less acoustically confusing for people in the room, but I would suspect reflections will be more variable on people, so the echo cancellation wouldn't be as effective.

Am I on a decent path here, or am I way off the mark?

Thanks,
- Alex

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