Thanks for comments on the DIY idea. Shane I do agree, I'm leaning towards the svs pb12. In regards to the 12" driver have a special sound, yes it certainly does in most situations. Obviously there are some 10" drivers that can sound as good as a 12" driver although they will cost more because of the extra points they need to compensate for lost surface area and added xmax. The amount of money used in its design to component this. Sure, You can spend 1,000 on a 10" sub. But for $600 I can buy a 12" sub that will sound as good if not better. One main aspect of creating bass is the goal of moving air, obviously a 12" has more cone area then a 10" driver.
My point being, that I want a 12" because of its value, and I really don't care what any tests on paper say..
a 10" does not have the same musical tone as a 12" driver, just like a 15" driver doesn't sound like a 12" driver. If a 10" subwoofer sounded like a 12" or 15" driver I have no idea why anyone would not want that, I mean they are smaller and more compact. Why in the world do people buy 12" or 15" woofers, heck lets all buy 8" woofers.
Specs or diagrams are cool and all, but ears do not lie.