Be very careful with this, some speakers will be greatly effected and others may notice only minor changes.
Check out Ascend monitor 170's and if you have the cash check these out:
http://www.mksound.com/satellite_speakers.html
I was looking into demoing the S-100B. There are others here but the above is a sealed design which helps with enclosures.
I emailed Paradigm on placing their Studio 20's on the sides and they said it be shouldn't be a problem. Their speakers excel on wide dispersion, and are close enough, on both vertical and horizontal axis' (according to the book and "honest" salesman).
Also, the front baffles need to be flush with the front of the wall unit else you will have some serious reflections inside the enclosure. Does the enclosure also have a front door or is it open?
Good Luck