Boom, your comment that "I don't listen loudly" pretty much answers your question in my view. The extra woofer of the M100 or high power woofers in the M80 provide a capacity for playing more loudly. The Axiom specs show no difference in bass extension(and none would have been expected), so the standard M80, which is already very good in power handling ability, should be amply sufficient for your needs.

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Enjoy the music, not the equipment.