Some advocate simply using it “In-line” and setting the crossover frequency to a suitable value so that the subwoofer reproduces the low bass sounds rather than the stereo speakers, but this allows the stereo speakers to reproduce the harmonics of the bass sounds the subwoofer is unable to.
What happens when you have an "in-line" sub is that everything above the crossover still goes to the speakers, and everything below goes to the SW. This is a GOOD thing, because the smaller speakers are ill-equipped to deal with those uber low frequencies. If you do not attenuate the signal in that uber low range, then they will still try to make the sounds, even if they cannot or only do so poorly. By having a crossover point, they don't even try, so the drivers are left with an easier load and typically do better with it. All that to say, by using this method, you will NOT be loosing any harmonics, as they occur much higher in the frequency spectrum, and therefore those harmonics will still come out of the regular monitors. The subwoofer will simply take the bottom octaves (fundamental, essentially).
I also echo that you'd want to shoot for a sub rated to at least 32hz (even at -3db) as that is low C of a 16' rank. The 32' octave is nice (fun) but not necessary, strictly speaking.