Ok, so i have a 1995 Ford Lightning with dual corbeau racing seats. Looking to add a sub box, the video/picture(s) below give you an idea of what space i am dealing with. I can get direct dimensions later. But looking to add a single 15" and incorporate a push button start, switch panel for my odds and ends, etc into the console/sub box i am building. Any ideas or picture of your set ups?

I chose a 15 vs dual 12's or 10's as i am not going for pow pow of a sub, i enjoy the clean vibration and something that rolls with the song. I listen to anything from rap to metal to country to jazz to classical. Very wide variety of music and i felt this would get the lows and hit the high bass levels as well and the 15" draws more rumble vs thump. Looking at a shallow JL Audio but open to suggestions. Again, this is NOT a THUMP THUMP listen to my rattle. I want this to be a CLEAN.. REPEAT CLEAN!!! sounding sub. My system is loud enough and with a proper set up i can get the bass loud if i want but as stated and emphasized again, CLEAN!

 

I have a box the width of the cab with 2 10" subs in it. Has room for 2 more, and I have the amp and capacitor mounted on the face of the box. I have JBL Power Series in there right now and they're very smooth. I have 2 more Rockford Fosgates waiting to go in. I also have bucket seats in a regular cab so I know all about limited space.

 

whatever setup you choose you should have a head unit that has sufficient controls for the subwoofer to do what you want it to do. a good head unit will control not only the sub's volume but frequency range as well, thats how you can get clean out of a subwoofer. If you have a lot of square inches of cone pushing a lot of air you tweak the sub's controls for a little less volume, and conversely if you have a single smaller cone. To eliminate all the rattle cut off the frequency response above the subsonic range. That way you feel it less and hear it more. good luck!

 

Got one of the best kenwood had to offer. Right now i have 4 co axle infinity speakers now. 2 6" and 2 6"/9". Running off a 400 watt quad channel amp if i remember right. Not home so not sure on wattage. Went for highest RMS feed speaker, head unit, and amp wise. Over all in my area and within the car guru's of my local area which is quite a lot i have one of the loudest clear sounding systems. I get compliments on my system before the truck it seems like now which most people comment on if they don't hear me coming first.

My Dad as a kid always told me its not how loud but how clear a system is that makes it worth wild. And i always look back and always have to say damn he was right hahaha.

But either way I am looking at subs that hit 25-500HZ, don't need anything lower than that and it will hit the frequency the co axle will not because of the highs thats in them the bass is turned down.

The head unit i have i can control frequency, sub on and off, sub power, individual speaker power, and with the 4 channel amp each speaker has its own channel and i can adjust as necessary from there. I have 100% control over each speaker. Biggest problem i can see is getting the amps to fit cleanly. Right now i am waiting to mount my current amp on the wall. It is leaning up against the wall and put wedged below the seat. But all i have to say is WOW about this system. Couldnt ask for more with what i have!

 

I bought and installed a fairly high end JVC (same company as kenwood and uses the same connecting block so I didn't have to rewire the block at all) I installed boston acoustics rears and infinity door speakers. It is also very clear but as you noted the standard size speakers just do not have the frequency response or sound pressure level in the low range that a subwoofer does. Here's a little trick that I employed that you might want to consider for your setup. The JVC has both a front usb plug on the face of the unit AND a rear usb plug on a 4' wire. I snaked the wire under the carpet, cut a small slit in the carpet where the cup holed meets the seat in the fully back position. I leave my 65 GB ipod under the cupholder out of sight. Basically I have a 10,000 song self charging music library stored under my cup holder out of sight. It works perfectly and I don't need anything plugged into the front of the head unit.
It seems as if you have done so good research on this subject and I would be curious as to what type of sub setup you end up going with. I have considered a few things in my own research and it has left me with a few questions: are the all in one 1200 watt single subs any good? some of them will fit behind the seat but nothing larger than a 12" sub. Has anyone tried the alll in one flat systems that can actually fit UNDER the seat. If they are capable of decent sound and sound pressure levels that would be ideal, i always have something behind the seat. but the only thing I keep under the seat is books of maps and I can easily put them under the pass. side since I do not need to access them on the fly while driving. Let me know what you decide upon, I will be interested for my own upcoming upgrade, when I get the money