Help with Ideas Please !

I have a 2001 Nissan Frontier Crew Cab, there is a little room behind the back seat, the biggest Woofer I've been able to build a Box for was a Kicker 8L5 in a ported box, it sounds ok for it's size but I need more bass ( I had 2 10W6 in my old car, so you understand what I am missing ) I was wondering if anyone has seen something or has any ideas on what I can build into that truck that will sound quite good but not take up all the back seat, half at most, ( it's a 4 door for a reason) or is my only option is to rip out the back seat and go all the way? Any links to pictures, or descriptions are appretiated in advance.

Thanks for your reply Andrew. I'm pretty sure that those 15's pounded like crazy however my interest was to try to get something that won't take up too much space and no cutting, yet would sound good. So if somebody knows which woofers would work best in very small enclosure (about 3/4 ft^3) with about 5" depth I would appreciate it. Here's an example (4 RF 8's) .

Dude I have a 2002 CC and am in the same predicament you are, I used to have a Punch 15 in my old car. I have spent many hours pondering what to put in. The box I finally came up with fits one Pioneer TS-W254DVC, I just barely got enough airspace for it. It's defintiley not a 15 but it is a DVC 10 at 250rms, I am going to run a jbl bp 300.1 to it (so it should sound aight). I had to get .80ft3 of airspace which was a biatch. I am actually going to install all of this on friday and saturday and I can email you what mine looks like if you want to check it out. I had to take out the metal flap that holds the jack, and the jack too. I am putting the jack in the truckbed in a toolbox thats going to be bungeed to the bed so it won't shift around. Although I bought a 10 DVC (before I decided to dremel out the metal tab) You could defintiley put one DVC 12 or maybe 2 DVC 10's with the right box design. I would go with a DVC 12 but thats my preference. The install should look really good, I have been doing this a while. I got a digital camera and I can take a step by step of what I did and send you my box design plans, let me know man,