So i was thinking about yhe whole slim sub idea too. What i have come up wit is a couple of things. 1. Ithink your better off with an 8 inch powered slim sub, for there dimensions are better. So the two companys i was looking at are pioneer and kenwood. Bothe have nice units under $145. If ones not enough u can put two. One under both seats. The other idea i been thinking about is that u dont get a powered unit. Then i beleave u can get away with a slim 10 under one seat with a custom box. Then you can get either a mono block amp under the other seat or get a 5 channel amp and power your sub and speakers. Then u still got your cargo space.