Bookshelf Speakers in Ceiling Corners?

The positioning is very tough. If you want to avoid boom you'll need to avoid large (and even medium-sized) woofers and anything back-ported unless it's been specifically designed to work up against the wall.

If it were me I would email George Short at North Creek and ask him if the North Creek Echo would work in this application.

http://www.northcreekmusic.com/

Another thing I would do is reconsider the sub. For lasting satisfaction, that money would probably be better spent on upping the quality of the main speakers.

There's similar bass gain at the upper corner of a room as there is in the floor+ corner.

I would put in the effort to tilt the speaker down enough to have some sound stage and imaging at your preferred listening position. I've heard speakers mounted and adjusted this way and it can work surprisingly well.

During the evolution of my home theater, back when my son was small, I had safety cables attached to the large bookshelf speakers mounted on the side and rear walls. This was not only for the safety of my child, but also because one side channel was directly above my (then) Versa Dynamics turntable.

There are professional speaker mounting systems designed for various loads and speaker sizes. I would factor that into system cost no matter what else you do.

Someday your toddler could be helping you wire up a new pair of floor standing speakers for this same room. Then the two of you can sit down and enjoy the upgrade together.

I'd go Bose acoustimass in this situation....the satellites have almost nothing below 120 Hz so not much modal issues right in the corner. Bose are a good design for a half decent sound in crazy placements.