@Darvin, Boss Audio is a good brand. But, since last 3 years I haven't been tracking it especially after encountering the low grade dups in bangalore of same brand. I got the same reviews by few trustworthy installers in chennai, mumbai & delhi.
If its genuine, its good in quality for sure. I used to love their amp kits once upon a time

Well, in my opinion, I would recommend atleast 10" sub. either from Polk Audio or Hertz. And put it in a 1 cu.ft. or .88 cu. ft. box. It booms. Check them out:
http://www.polkaudio.com/caraudio/db/index.php?s=db1040and
Hertz - Energy series - ES250 (
http://www.hertzaudiovideo.com/default_en.htm)