Ok, here's my first barage.

People who buy subwoofers purely on spec, or reviews of the subwoofer are
completely screwed. The only simple way to evaluate a subwoofer for YOU is
to put it in your room.(*)

The reason for this is that subwoofers, more than any other component, are
most subject to the effects of the room they are on.

75% of the sound of a subwoofer is really the sound of your room and the
placement of the subwoofer in the room. Only a small amount of the quality
of the perceived sound with a subwoofer has to do with the subwoofer itself.

One of the worst mistakes that consumers make, IMHO, is to look for the
"best" subwoofer they can afford, without knowing how that subwoofer will
work in their room. That is, the "best" subwoofer in the world, can sound
like bird poop hitting a car roof in the wrong room. An "average"
subwoofer, hundreds if not thousands of dollars less, which matches the
room, can evoke the fear of God and the joys of spiritual and physical
ecstasy.

A room with very pronounced 20 Hz resonances due to room dimensions really
would benefit from a smaller sub, one with a cut off at 40 Hz and 4th order
high pass response there, allowing the user to hear ALL of the bass, from
the satellite speakers on down, not just the room resonances. But in this
SUV world, no one really wants to hear that. More more more, that's what
we want, to reach perfection via the credit card instead of self
exploration, or self knowledge. When we can purchase another 0.01% lower
distortion figure. then we know we are on the path of virtue and truth.
Bleah.

(*) There are other ways to evaluate the sound of a room, and the match of a
speaker in it, but this involves tools usually reserved for architectural
acousticians, and implies that you have an accurate model of your room, as
well as an accurate model of the subwoofer being considered, which except
for professional speakers, is a rare thing indeed.