Yes BK is a reference to Butt Kicker. But Butt Kicker is a name brand & yet there are other brands that make similar products. My Earthquake Sound model is MQB-1, if I just referred to MQB-1 nobody would know what I'm talking about so I called it a "BK".
Yeah the Earthquake amplifier I use to power min has, Crossover, Phase & Volume knobs to help dial it in properly. Makes it nice! What I like about the Earthquake better than the BK is that it doesn't set on the floor & under one leg of the couch. Instead, you mount it to a support beam of the couch. I turned my couch upside down, removed the bottom black fabric & mounted it to the largest wood support right in the middle of the couch under your actual butt. This makes the whole couch shake evenly. It's a little more work but you don't see anything & since I mounted the little amp to the underside, i have a mobile vibrating couch!!