Which Speaker should I buy?

My Onkyo puts out 65 watts per channel and my room is about 18x16 ft. I have already purchased a Polk Audio Center Channel and they have 3 matched speakers I am looking at buying to round out my 5.1 set up.



http://www.newegg.com/Product/Product.aspx?Item=N82E16882290042 This is an in wall 8 inch



http://www.newegg.com/Product/Product.aspx?Item=N82E16882290201 This is a Bookshelf



http://www.amazon.com/Polk-Audio-RC80i--Ceiling-Speakers/dp/B00006BMQT/ref=sr_1_1?s=electronics%26amp;ie=UTF8%26amp;qid=1302788461%26amp;sr=1-1 This is an 8 inch in ceiling



It seems like there are lots of good deals out there on Polk stuff thats why I choose them. If I get the bookshelves they will be used as the fronts with one of the others being the rears. I was fine with saving a little dough and getting the ceiling speakers, but I have read the the in walls preform better because the woofer and tweeters are separate. I'm excited about the project and really prefer to do all in ceiling's, my living room has trey ceilings but instead of step up like you see in most trey ceilings int is a straight 45 degree slant which would be great for imaging and be visually pleasing. My expertise is limited, but somebody out there always seems to point me in the right direction.Which Speaker should I buy?
Because of the size of your room and the wattage you are using I would get the largest most efficient speakers you can afford..personally I would prefer Bookshelf speakers or floor standing speakers to in wall units due to flexibility... in wall speakers once placed there is not too much you can do to tweak them...bookshelf speakers can be towed in towed out moved a couple of inches to the right or left...you would be surprised what just a little movement like that will have on the quality of the sound they produce...also they can be upgraded at a later date...