Got my 15's the other day as well ....
I'm going to toss them into a couple 3.5^ft @32hz boxes I have already, and get them broke in good, and see how I like them vented. I have come up with a couple bp boxes that they really seem to like, on term pro ...A have a dbl loaded 6th order that will play from 24hz to 83 hz with 6db of gain I might try out in the truck ....
24 and 83 are the 3db down freqs, it's flat from about 32 to 74 hz. So I'm kinda concerned about cabin gain/res freq making it peaky ....