If some installer can get a wire from the front avr through the front wall and then across the ceiling to do a ceiling mount he is surely good enough to go another 16 to 18 inches to do a ceiling mounted bookshelf, even if a minor patch and spackle is required at the speaker area. In the long run you get exactly what you want. What is above this ceiling, if it is carpet on the second floor cant you remove it from the tack strip and cutout an access hole in each bay where the speakers will be below, How will the installer get the wire at the front wall up inside the wall and through the wall plates and into the ceiling joist cavity without patching drywall.