What about a sub in the spare tire well? I know people who have done them and were happy with the outcome. You do lose your spare tire, but as long as you arent' planning on doing any road trips, it may not be a bad trade. I personally like the enlclosures that fit along the side of the trunks and wrap over the wheel wells, they get good sound (if built right) and still leave the majority of your trunk available for use.