It depends. For music, 30 Hz + is pretty much 99.9 percent of all recorded content. For movies, it depends on what kind of movies you like. On newer action and science fiction movies, they can take advantage of lower frequencies, but they will still mostly be using frequency ranges above 30 Hz. Other types of movies obviously don't really use super deep bass.
If you have a variable tuned sub like a Hsu, Monoprice Monolith, Outlaw, or one of the upper tiers of SVS, you can see what you are missing pretty much in real time since you can switch tuning frequencies in the middle of a scene. Get a variable tuned sub, and then throw on a movie scene that has a constant stream of very deep bass. A great scene for this is the 'pods rising' scene from War of the Worlds. While the earth is opening up in that scene, toggle the EQ switch and then open up or close a port that corresponds to the EQ filter. That will let you know what you get from subs with various low-frequency extensions.
