"I have a "T-Rex" audio track that is much more impressive with a sealed box woofer than a ported one even with the ported box having a lower F3. You could definitely hear T-Rex stomping through the forest with the ported woofer, but the sealed woofer provided more bass you could feel and shook the house more."

I'm going to have to dig up my Jurassic Park DVD and try that.

My current subwoofer is an old 15" down firing passive unit sold by DAK many years ago. It has dual 6 ohm voice coils and a speaker level cross over. It's a sealed box measuring about 20"x20"x24" on the outside. Currently each VC is driven by it's own channel of a Niles Si275 amp (which results in almost 100W/channel into 6 ohms). Both channels of the Si275 are driven through a Y cable from the line level sub output of my Onkyo '702 receiver. The sub can really rumble.