In addition to what Mapman states, the power requirements for high sensitivity main speakers and a sealed subwoofer are exponentially different. It takes an enormous amount of energy to move a driver reproducing low bass in a small sealed enclosure, no escaping the laws of physics. With the necessity to double power for every 3db increase in volume, you can quickly run up a big power requirement deficit with the particular engineering requirements for a sealed sub. I've seen a number of ported subwoofers with plate amps that have 1/10 the power of sealed subs.
Does sensitivity matter in powered subs?
In a low watt, high sensitivity rig, it seems wrong to hook up a 500+ watt powered sub woofer. I see some subs include specs on sensitivity, but many don't mention it, and there has been little discussion on it that I can find. Thoughts? I am asking both for my own system but also as a general inquiry. Thanks.