Dear self: research this article more and calculate the amount of polyfill you need to put into your box.

http://www.audiojunkies.com/blog/1348/u ... e-resource

You have a 1.5 cu ft3 box. Your woofer idealistically needs a 2.5 cu ft box. This probably isn't going to happen, but you can get it to approximate a 2.0 cu ft box.
http://www.parts-express.com/pe/showdet ... er=260-630

If I calculate right, I think I need 2.1 lbs of polyfill. And some sort of way to keep the polyfill from shooting out of the vent. Maybe some speaker grill cloth or something. Look into what people are using for this material.