Start here and come back when you have more questions come back.
http://www.caraudio.com/forum/search.php?searchid=2475450
I believe with FI as you go up the line from SSD-BLT you get more SPL oriented speakers, not sure but that is what I get from what I have read with the most common around here are probably the BL and BLT.
I am ordering a 12" BLT shortly myself, before you ask what the best options are do a search I just read through pages of the same thing last night so it has def already been asked //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif
http://www.caraudio.com/forum/search.php?searchid=2475450