Monoprice Monolith THX 13" Audiophile Grade Subwoofer for the Extreme Bassaholic - YouTube
Amazon.com: Monolith THX Certified 8in 150-watt Powered Subwoofer, Deep and Powerful Bass, Compact Design, Quick and Easy to Setup, for Home Theater or Gaming Systems : Electronics
M&K Sound unveils new line of THX Certified® reference subwoofers