I listened to the pioneer 12 in a shop and it was impressive. It was in one of the factory boxes that had been torn apart and rebuilt. I would compare it to the 4 of my 8's running on 500wrms. Don't have a termlab but by a rough estimate people generally come to the consensus that my 8's are about 120db. Give or take a few of course.
Kenny, how bout Premier's new woofer? Its not a shallow mount but its pretty compact and seems to be similar to the ts-w3004/2's. Its got some new air suspension system that allows it to be used in a very small enclosure (.5-1.0 cubic feet) I saw it somewhere online for i think $135.