D, using the M22s to play material that should be imaged in the center has to create a "phantom center" midway between them because that's what happens when two widely separated speakers play the same sound. The image will stay centered for a listener midway between the speakers, but will shift in step with the listener if he moves to the side. A center channel speaker keeps the center image centered even for listeners off-center. Experiment with the M22s without a center; it's what I use.

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Enjoy the music, not the equipment.