Basic question that I thought should go here rather than the speakers / subs page. Am I understanding correctly that an "active" subwoofer has its own power supply and plugs into wall power in addition to receiving sound voltage over the speaker wires? The advantage is more power available to move the cone - yes? Thus, a "passive" sub uses only the power on the speaker wire to move the cone - just like regular speakers? If I'm understanding correctly and I'm ready to buy is an "active" really that much better than a "passive?"