Congrats! Great to know you're enjoying your music. Do post the pictures
djay, this is a common problem with free-air subwoofers, you need to take care of the boot in the best possible way, otherwise it rattles. All you have to do is damp the boot, as completely as possible.
You can find the damping thread here:
http://www.team-bhp.com/forum/produc...er-thread.html (The Damping Material and Sound Deadener Thread)