Part of the subwoofer learning process, is knowing where one wants to go. Have you looked at the first couple of posts in the ULF thread I linked to?
As we all know, knowing what one's expectations are, then they can narrow their field of study to that what serves the best.
Have you checked out the first post in the "The New Master List of BASS in Movies with Frequency Charts"
Believe it or not, my questions are designed to help you learn about that what you seek. ...