Thanks for posting the picture... If I were to build a box I would definitely use an 8-10" sub based on how much volume I could get. bigger is not alway better if the box cannot be sized properly. I've built a lot of speakers in the past and I have the woodworking skills to build almost anything... but I have other woodworking projects in the queue.

I'm trying to avoid having to build a box. While the stock don't look as meaty as the JL units.. they really don't look that bad. Did the stock system sound that bad? Maybe I would go to the dealer to listen to one.. Maybe the stock sub with a good quality amp will get me enough bass .. and if not I could always go the route you did. Thanks for the help!