beetlemania,
Until I win the lottery, I'm going to put my money where >99% of the musical content is.
That makes sense in one way of course. But it does miss some of the major reasons why people integrate subwoofers. A sub tends to change (and if done right, enhance) the sound almost across the board on content, even when there isn't obvious deep bass content. Having experimented with my subs, I've found that to be true. In most content soundstaging and dimensionality increase when the subs are on. And then there is the purported benefits of crossing over the low frequencies to a sub,. Relieving the main speakers of doing the low frequencies is supposed to lower distortion in the main speakers, make for better performance, more dynamic, less restrained etc.
I haven't tried using a crossover yet so I can't give my own report on that, but I do have a great crossover to try, so I'll report how things sound if I ever get around to adding my subs :)