My last setup I looked for exactly what you are looking for. I wanted low low frequencies. Im talking where you can actually feel the sub 10-20hz, lower than my 15HC in a sealed box did. My car moved. Find yourself an Avalanche and build a atleast a 3cu ft sealed box. Make sure the box doesnt flex and seal it to perfection. I had to glue gun about half of the screw holes after my sub was in. This setup was too low for me though. I listen to strictly rock and lost a lot of kick from the sub. The quiter low notes would always greatly over power any other bass frequencies. Im going back to a smaller box, but it might work for you depending on what genres of music you enjoy.
