I want good bass in my car but I need the cargo room for my stuff?

I have a 2005 ford explorer and the speakers in it are okay but don't produce good bass or any bass at all and I was wondering if there are any good speakers that I would just put in the car doors for better bass or is there some way I could put a sub in with out taking up any cargo space like a stealthbox or a shallow sub that won't take up space so I can still listen to my music with bass but still be able to have my third row seating up and have space to put stuff in the back I could really use some help with this I have no idea what to do. What would be the best way to go for my car?

JL Audio makes a Stealth Box that comes with a single 10" W3v3 subwoofer that's the same color as your interior. It's a slim design that will fit great. Just get an amplifier and mount it under your passenger seat or somewhere similar and you're set.

http://www.crutchfield.com/g_530/Vehicle-specific-Enclosures.html?tp=113

Kicker does make a few different powered woofer combos. They have the amp, box, and sub all in one. One of them you can fit under a seat such as the hideaway.
http://www.kicker.com/powered_subs

Sure there are some speakers that put out more bass but typically at the cost of your highs and or needing a amp to power them.

The other options you can build s a custom box that will take up the surface of the floor any where from 4" to 13"in. It all depends on the size of the woofer and the box.
Like a inverted wedge box keep the protected at all times becaues it firers down to the floor and wedges it to create more bass. The box is then not to high.
or something like the Wicked One or Low Rider keeps the woofers protected but the woofer face strait. So the box is high as the woofer and is really deep and wide.
or you could just go with a simple box and make it compact with small woofer not much space needed.