I can careless about SPL myself. The w6's still provide more output than I'd possibly need. They are nice subs, but I don't think they are superb. There are many other manufacturers out there, like image dynamics, who's subs sound superior. Very tight, accurate, and at a lower price.
The w6's are good in their own right, but stacked against some of the competition at that price point, I don't find them entirely justified.