Since most subwoofer talk is partial to size and power, let me go the other way.

I just noticed that most computer subwoofers are really small, usually the size of a shoebox. (i.e. the one for the logitech z-640)

I have already have a subwoofer, but it robs the backseat of 2 passengers (it's a pickup truck). A subwoofer the size of a small box would tuck nicely in a corner. I might inquire at araneta auto center if they can fabricate such a subwoofer.

I've considered powered subwoofers, but decided against it, since I already have an amplifier.

I really don't care if it can't boom outside, since I'm more concerned about interior car entertainment.

What would be a suggested brand of compact subwoofers out there? I'm guessing it'll be 10 inches or even less.

Would a subwoofer of such dimensions be better of being sealed or ported?

and what would be the tradeoff for the size, aside from the loss of volume?