If you can squeeze in about an extra 1/2" of depth, I would go wtih a single Mach 5 Audio MAW 15. It should give you good output (definitely more than te Sonys), but if you can port it, you'll get even more.
Get one for $80 shipped here:
http://www.soundsolutionsaudio.com/shop/index.php?act=viewProd&productId=50
I could have sworn shipping was included in those prices. Can't remember where I heard that, but I know I did.it's not $80 to the door