o crap I had 12 of the 12s on 6 arc 2500s' in a huge clamshell. I had 2 of the 15s to start on a 400 watt blaupunkt amp. I still have 1 of the 12s left and its still going after just a refoam in my little brothers car. nice moofers.
Mine killed around 25hz - 40hz in 3 cubes sealed, back then on the Alpine IASCA test CD. You could do a smaller enclosure if you wanted to raise the response curve.