I used to have three JL Audio 12" subwoofers and a JL Audio 500 watt amp w/ a capacitor in a huge ass box that took up the majority of the trunk in my 1992 Explorer. When I sold that and got my 1996 Eclipse, I put two of the subwoofers in a spacesaver box with the same amp and capacitor and gave the other sub to my brother for his car. The whole setup was actually stolen once out of my Eclipse, but fortunately, insurance covered the loss and I got brand new equipment (the same stuff). When I sold the Eclipse, I sold the subs and amp to a friend of mine. While I enjoyed them, I think my subwoofer days are now over. It was fun setting off car alarms, but I'm sure I suffered a good bit of hearing loss because of them.
...and I actually have a picture of the Eclipse setup. Note the neon tube mounted above it - it flashed red and pulsed with the bass (somewhat embarrassing now, but I thought it was pretty awesome at the time).