So I will be ordering an OA-12v2 D4 very soon after selling my current system (Upgrading from a Fosgate Punch P2 12, 2011 model). I have a Rockford Prime P500-1d to work with, so the sub will see just over 500 watts. I have read in many places that the more power, the smaller that the box can be, and the less power, the larger you can build the box... generally. So I was thinking of doing a 2.5 cuft enclosure for the OA, on the 500w. It will be going in the trunk of my 2000 Civic sedan, most likely sub back, port side. Does this sound appropriate? Is there another way I should approach this? The box will be tuned to 30Hz via 4" aeroport. Thank you for any help, and I apologize if I left out any important details.

That would work rather well, but in all honesty I would utilize a slot port in your application if you have the space. You can adjust port area and volume a bit to help make the enclosure more efficient. This would help with getting more with less in a since.

If you are limited on space and/or plan to upgrade power, I would slim the enclosure down a tad.

That would work rather well, but in all honesty I would utilize a slot port in your application if you have the space. You can adjust port area and volume a bit to help make the enclosure more efficient. This would help with getting more with less in a since.

If you are limited on space and/or plan to upgrade power, I would slim the enclosure down a tad.

What amount of port area would you recommend in this application? It is a daily driver setup, and I'd like as much bandwidth as possible.

Design the enclosure for desired response, not how much power you are running.

http://diysubwoofers.org/misc/portcal.htm

That website gives you the formula for recommended minimum port area.

That website is very helpful, thanks a bunch.