You should match the speed and sound of your sub to your main speakers. Use an electronic crossover and set it at the correct point and slope for integrating with the main speakers. Make sure that the sub will go as deep in the bass as you want to go. I've seen many subs that only go down to 40Hz, and that is not much of a sub. To drive it well, you'll need some good strong power, as bass frequencies require alot of power to get high SPL, and most subs are not real efficient, and some have equalization built in, which will need even more power.
