Actually, it's not a bad idea, or a new one. By center, I assume you're referring to a d'Appolito design: one tweeter flanked by two woofers. My CLR-2000 center is perfectly suited to use as mains.

The only real "no-no" is that this type of speaker, because of its dispersion pattern, is best oriented vertically, and most people lay them down. Also, they're almost always 'mono-polar' (front-firing only).

Larry
www.fineelectricco.com