Do you mean like a free-air setup? Not sure how that would sound if that's what your talking about.
You should checkout http://www.subee-sound.com. I'm not sure how much bass your lookin to produce but I like the trunk corner they have for 1 10" sub. They do have a version for the new age wrx but it's not listed on his site yet. You can email them for more info.
They also have other cool setup's.
Hope this helps