Powered in-ceilings tend to have their own AC cord, so you just need to find an outlet for them somewhere. That particular one says it is DC powered, so yeah, a transformer would have to be involved.
As for the dock, anything that can control the volume for headphones should work for the speakers, but hooking them up to the source would have to be addressed (might need some specific adapters.) In-wall/in-ceiling speakers usually aren't designed to hook up to a 3.5mm jack. Also, does that dock even have a line-out?
Personally, I'd go the receiver route, as I know it could be made to hook up and work.
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