Yes you can put in wall speakers in the ceiling. They are of the same design. I would how ever not recomend it though. There are some awesome round 6.5 inch 2 way speakers (even some 3 way) that would do the job more than well enough for music listening. Plus you would not have a square speaker in the ceiling. I bet the fasion police (aka wife) will be more happy with a less obvious speaker than the bigger square one. Plus if you have recessed lighting in the ceiling, a square speaker would clash as far as looks are concerned. round,square,round etc......
Take a look at: Niles, Phase Tech, Earthquake these companies make a good inwall/inceiling speakers.