Lots of great info in this thread. I saw some unanswered questions along the way, but I don't know that the original posters are still around, so I won't go quoting/answering. As I'm trying to get back into car audio I'll be frequenting the board more often and can help answer them as they come.
For the record, I agree with the few posters in here that have said there is almost no case where a sealed box will perform better that a ported box... only when faced with huge size constraints would I sacrifice the efficiency that the ported box brings to go sealed. Efficiency can go a long way to improving sound quality, especially with the mammoth subs a lot of you SPL guys run.