Can the human ear even hear below 20hz?
So, as an example...
The Hitchhikers Guide To The Galaxy (movie) has a section where they are all on the bridge. At one point, my entire room started to shake. I didn't hear anything and was wondering WTF was up. Then I realized what it was. It was a subsonic audio signal that I couldn't hear. One of the first I recall ever noticing. I jumped back a minute and played the same section again. Sure as heck, my walls and couch began to shake again at the same point.
Neither my wife, nor I, could hear the bass that was playing back. But, my subwoofer faithfully replayed that section on demand.
This is, of course, using a Velodyne HGS18BG subwoofer which is well over $1,000 and not in the budget for everyone. Still, it is quite the impact that is possible. Truly room moving sound.
A cheaper option, which continues to blow people away during movies, is using tactile inducers (Butt Shakers for example) to deliver the true feel of serious bass directly to your furniture. I would strongly recommend it for any theater setup.
