The driver that Steve uses per my recommendation is not by any means normal. It has a motor system that is very unique; a LMS motor designed by T.C. Sounds/Audio Pulse. This 12" driver has more real (verified by 3rd party analysis) linear air displacement capability than most 15" good quality drivers! It is especially suited to sealed cabinets (
very simple to build if you wanted to DIY your own box, and with relatively small size) of about 3-4 cubic feet each. It requires one parametric band of EQ to compensate for the response error of this size box. The O Audio branded 500 watt BASH amplifier is perfect. It has the parametric band for the correction, and is very high quality, and produces sufficient power for the driver, although even more power would be beneficial. Combine this with the pre-made/pre-painted 3 cubic foot cabinet from
www.partsexpress.com and you have a subwoofer, that for about $700-$800, will surpass anything commercial/retail for the same price in so far as overall sound quality and SPL levels, averaged, are concerned.
-Chris