I have a question. You said its better to use vented boxes in a car? I dont understand. With the car's transfer function, you should get great bass extension with a woofer in a reasonably sized sealed inclosure, say with a qtc of around .707. I would imagine that the Eminenice Alpha's would need a vented box, since they are not designed as subwoofers and have a high FS. But for those rockford fosgate and JL woofers, they should go reasonably low in a sealed box. Now, .25 cuft may not be enough, but somthing around .75cuft perhaps? If he is looking for sheer output, then yes, vented would be best.

Oh, Mitch and I put my 18" subwoofer in my brothers car. The really big one that we were talking about last time. It is horendously loud. I think you would like it! :-) Also, has that pair of 2pi's been built yet?