What is your budget?
Are you doing in-wall/ceiling for a cleaner look? Do they have to be hidden? There are more options if you don't use this type and better sound but in-wall speakers are much better than they used to be.
With ceiling surrounds, they need to be somewhat directional. Some will drop down a little to achieve that. Some you will be able to angle.
An example of this is these Paradigm speakers:
http://www.paradigm.com/products/pr...eiling/signature/signature-series/sig-1-5r-30. Paradigm makes very good speakers for the price.
Also with those ceiling placements the fan might be an issue. I can't tell if that is a shadow or a gable ceiling on the left but that also might be a an issue with ceiling mounts.
With location C, because they are in wall, they will also need to be somewhat directional. Something like this would work but a little more high end:
http://www.legacyaudio.com/products/view/deco/. Legacy isn't a company that is well known but makes fantastic speakers.
My advice is if you don't have do to in-wall/ceiling then don't but we are talking about rear surrounds so they aren't as important compared to the fronts and center speaker.
Some more information would be helpful on what you are using for electronics and/or HTPC and budget.
Happy listening, the Prisoner
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