The big problem with in-ceiling for the front speakers is that they will be severely off-axis at the listening position, exhibiting significantly reduced highs and resolution. To get an idea what I’m talking about, go to any retail store and listen to the music standing directly underneath a speaker, compared to what it sounds like 20 ft. away.
Bottom line, in-wall speakers facing the seating position is a much better option, if you are dead-set against having speakers physically in the room.
Regards,
Wayne A. Pflughaupt