MartinLogan Dynamo 300 8" Home Theater Subwoofer for $109.99 shipped after promo code EMCJNGN237.  Here is a screenshot for your reference. This subwoofer features 75-watt amplifier with 150-watt peak output, low-distortion, low-turbulence port for extreme bass output, and a high-density cabinet.  Most places have it for about $299.