If you want to hear what the JL Stealthbox sounds like give me a shout and you can check it out in my 98 GMC Extended cab. The Stealthbox came with a JL 10W0 subwoofer installed and I have it hooked up to a Linear Power 2202IQ with a good Audiocontrol crossover. That amplifier is WAY overkill for that box and speaker, but it sounds pretty good unless you try to pound it like its a pair of 12's. I too wanted to keep the spare tools under the seat and that was pretty much the only way to do it with that body style truck.
Im in Duncanville. If you wanna check it out shoot me a PM.