Yes, the JL Audio Stealthbox is the way to go. I looked into this one quite a bit, and came upon my decision. I believe that MTX makes a box that holds a 12" sub, but it takes up the seating space behind the center console...it's also fairly easy to remove (steal if anybody had the chance). JL Audio also makes a box that encloses two 10" subs underneath the rear seat, it's nice, but it takes up the little bit of storage under the rear seat. The JL Audio Stealthbox is under the center console...it actually replaces the center seat, which means you don't lose any storage/seating space. It bolts down in place of the center seat/replaces it. It takes a while to install, but then again, nobody else can see it either. The center seat will be a bit tougher to sit on, but then again, it's my truck, I don't ride in the center front seat...or any other seat than the drivers seat! If you check out the Dodge forums under Stealthbox's (it's one of the ones on fire), you'll see the number of people who responded to this question before. The box is badass. I'm currently running the S4.600 Lightning Audio Amp, that puts out about 500 watts to my sub, and about 100 to everything else. I'm also still running my stock deck, so everything is hidden. The really nice thing about it though, is that if you turn up the bass, and the music that you play has enough of it (thanks to the downward aim of the speaker) you'll get a great back massage.
My project, '98 Ram 1500 Q-Cab 4x4
360/auto. K&N Filtercharger, Flowmasters, 3" Pro-Comp Stage 1 lift, 315/75/16 Big-O XTs American Eagle 16x8 rims, Optima Red Top, a nice little stereo...and the project continues.