Ok, here's my situation. I just put a new amp onto my 12" old Eclipse sub. I can't remember its model number, but it was there lowest model with a regular polyproplyne cone, not the aluminum or titanium models. Its about 5 years old now. I have it in a pre-fab standard looking trapezoid box. However, the box isn't big enough for the sub and its Q is really high right now and kinda sounds like ***. It plays loud, but I looking for more quality. I used to be very well versed on the subwoofer market, but I haven't looked at the market in 4 or 5 years now so I'm wondering what's out there for decent 12's that sound good in a small sealed box. If someone can remind me of the math formula used to calculate the volume of a trapezoid, I'd be appreciative. I can then give my exact cubic ft. requirements. I can give the woofer about 500 watts. I would like it to be able to play loud of course, but I'm primarily looking for an improvement in quality. My budget is $150, New or Used.