Point of fact: Mr. Mihaita is right that actual music hasn't very much content below 40 Hz, but that statement is about like saying that among all the music ever written not very much is by Bach or Beethoven. The fundamental of the lowest note on the piano is 27 Hz. Few piano scores include it, but any composer might agree it's nice to have it available, and a recording of a piece with that note, played on a concert grand piano, is going to be more convincing if the fundamental is audible on playback.
As for "maybe organs..." - yes indeed, organs. Bach used lots of pedal notes, especially for dramatic effect. I'm sorry for anyone who hasn't heard the Toccata and Fugue in D Minor and envious of any grownup who's hearing it for the first time, especially a live performance on a good instrument in a big space. (Talk about mind-blowing - !) And try listening to the beginning of "Also Sprach Zarathustra" (used in "2001") over a system that really lets you hear, as most theater sound systems of the time could not, that 32.7 Hz low C on the organ pedal.
Mr. Mihaita, I get Audio Advisor and maybe I've talked myself into following your advice on the Sunfire sub to go with my Magneplanars (lower limit 40 Hz).