Thin subs aren't the only option in our cars, you have to realize that if you're going to the trouble of a custom enclosure, it's easy enough to make it fit where you want it. So many people try to cram too much speaker into not enough enclosure and it ends up sounding crappy. I've heard a single eight inch sub pound harder than a 12, it's just all in the enclosure design and installation.
I have some experience with the W7's, and in my opinion they sound too breathy. i.e. moving more air than it was making sound. It could've just been the enclosure, but I'm pretty positive they designed it to spec. I've heard, but can't confirm, that the W6's sound better in many people's opinions. For the money you'll spend on a W7 you can get a handbuilt and top notch Digital Designs sub that will literally blow just about anything out of the water. Never have I heard subs sound so clean at any volume level as I have with DD subs. Do your research and find out what best fits your needs, it may be something as simple as an infinity basslink that just drops right in.
Just to rub it in, I've got a hardtop, so I get to put crap all over the place
Still dirty, all of the trim panels and tuning will be finished tomorrow, then some proper pictures will be taken.