Audio Systems: Stereo Speaker Sizing, yamaha htr 5940, ceiling speakers

Question
I own a Yamaha HTR-5940 Receiver which is 350 Watts and am remodeling and I'm going to purchase built in ceiling speakers.  I'm going to use my existing Bose Center Speaker, which is 100 watt speaker, located in my entertainment center.  I'm planning on installing my front right and left speakers above the Entertainment Center spaced about ten feet apart and a foot out from the entertainment center.  The rear will also be ceiling speakers spaced about twelve feet apart and about a foot our from the wall.  I am also planning on two additional speakers located in an adjoining room with a wall volume control run off the "B" speakers on the receiver.  In addition I hope to add an in wall subwoofer, probably in the wall surrounding the entertainment center which is a nook the entertainment center slides into.  The overall room size is 16'x16' for the main room and 10'x10 for the dining area.

My question is what size (both physical dimension and wattage) speakers to get for the six in the ceiling speakers, and the subwoofer?  My house is very small (a cottage really) at only 700 square feet total, so I think I'm just fine with the size of my receiver.

Answer
Generally speaking most manufacturers of in consumer ceiling speakers make drivers 6" to 12" in diameter. My experience has led me to understand that most in ceiling speakers use the dry wall that they are mounted in as a baffle. Judging by the room size I would say that even 10' x 10' is a very large area for a baffle. Moreover the larger the driver the more it focus's. As such I tend to like smaller drivers because they add less coloration of their own to the sound. Seeing as how you are planning to use a subwoofer the low end should be covered by that driver. The opposite is the case with the subwoofer. You should try to find a larger rather than smaller driver for that speaker. mind you in each case I am referring to in ceiling or in wall speakers.
Make certain that your receiver filters the sound to the subwoofer as well as the satellites. If your receiver does not have a dedicated subwoofer amplified output then you will need an ampifier with a built in crossover below 125hz.