I have a feeling that hanging an in-wall speaker in the ceiling is going to have a worse dispersion pattern than speaker designed for in ceiling use.

I'd do everything I could to avoid using in-ceiling speaker, but if there was absolutely no other option, I'd go with these from JBL: http://www.jbl.com/EN-US/Products/Pages/ProductDetails.aspx?PID=LS360C

Note that a pair will cost you double what a pair of QS8s cost, and they won't sound as good.

Pioneer PDP-5020FD, Marantz SR6011
Axiom M5HP, VP160HP, QS8
Sony PS4, surround backs
-Chris