Mike, as the previous replies indicate, it's unclear even with your explanation what possible benefit you could expect from what you propose. The voice coil has nothing to do with it, but connecting only the center channel output to the EP500 certainly would be "inefficient use" since only the low bass information in the center channel could be played through the sub. The more important low bass would be in the main left and right channels and there would also be some in the surround channels on occasion, which should also be played through the EP500.
