JD, welcome. 1. Speakers designed to be used vertically have significantly poorer dispersion patterns when used horizontally and this should only be done as a last resort. 2. The sub, assuming that it fits the space, can certainly be placed there, but it may cause audible vibrations in the wall unit. In addition, that would rarely be the best location from the standpoint of smooth and strong bass response, which typically would be better in a corner. location.

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Enjoy the music, not the equipment.