I'm not a fan of In-Ceiling speakers for surrounds as they don't surround you like a true surround speaker. The Qs8's point towards each other and wrap the sound around you, that is what you want. If the wiring is run to the ceilings, you might be able to reuse that wiring and figure out a way to mount the Q's to the ceiling.
In regards to B&W, my only exposure is when I almost purchased the B&W 703 floorstanding speakers, that is until I heard the m60's and m80's. For less than half the price, they sounded as good or better than the 703's. I would think any of the bookshelf speakers in the Axiom line up would perform better than those smaller speakers.
