I'm selling my subwoofer setup since the stereo is all out of the car to save weight now. The setup works great. It isn't pretty, but it's hidden very well under the rear carpet. It is about 3 or 4 years old now. This weighs a bit, so a local sale would be preferred, but I will ship it at buyer's expense.
The speaker is a 10" MTX Thunder 6000. It's never been over-driven and easily fills the cabin of a Subaru. It's built into a .67 cubic foot sealed enclosure (3/4" MDF) for a really crisp bass sound. There's a false strong speaker grill and a false floor to smooth things out, so that you won't know it's there when the cover is over it. You can still load up the wagon with tons of heavy stuff (and I have) without worrying about the subwoofer. The spare tire is in there and the subwoofer fits snugly inside.
I'm looking for $175 or best offer for the subwoofer, enclosure, amplifier, and false floor. There's one picture below, but follow the links for better views.