Fog, it may help you to understand that getting the last few Hertz out of a sub is an expensive proposition.

It takes 8 times as much power and moving air to make 20Hz sound as loud as 40Hz for example. Along with more power, this requires a larger enclosure. The challenge is of course that as you make the enclosure larger, you need even more amplifier power and a larger driver motor with greater excursion and power handling capabilities.

I'm slowly reaching the conclusion that sub sound is a matter of personal taste. Many out there for example like the sound of a "softer" sounding sub that has a lack of presence, kick/punch but nonetheless reaches down very low and tickles your gut. Others like a "harder" sub (which may or may not go down very low) that belts you in the chest.

Wouldn't it be great to have a sub where you can switch between hard and soft depending on mood and/or material?

House of the Rising Sone
Out in the mid or far field
Dedicated mid-woofers are over-rated