Just moved from a house where we had installed a small HT system in the master bedroom about 18 months prior to our relocation. The speakers included all B&W Speakers: 2-CWM650s as r/l fronts (in wall), the Cinema Series dedicated Center Channel (in wall), and 2-CWM500s as rears (in ceiling). These were driven by a Rotel RSDX-02 (combination a/v receiver with DVD-A)...a nice system for a room size of 17' by 13'. The B&W in-wall dedicated Center Channel provided crisp, clear dialogue...more so than adding another CWM650. I've also heard the CWM800s and B&W's higher-end in-walls...all were outstanding.
I've also owned RBH in-ceiling speakers in two other homes, and they did an excellent job as rear surrounds but haven't used them in an application in any other form. To my ears, the Polks sound dark and veiled...they didn't throw as dynamic a soundstage for movies and didn't sound quite as good in music applications (with DVD-A and redbook CD) as the B&Ws or RBH speakers. Another worthwhile contender for consideration: Triad speakers.
Good luck with your HT project!