I have a 15" 05 XXX and a set of the newer XXX components I've been thinking of letting go. And I'm right up the highway from you. Let me give this some thought.
The 06 is a LOT bigger. It has more xmax (almost 2x as much), higher RMS power handling, more total excursion (by 1.5" lol).... its just a lot bigger/nicer sub.