What kind of subs & amp do you have? There is alot to making good sound besides just changing the box, the components your working with play a big role also.
Thats the nice thing about fiberglass is you can form to any shape/contour of your car, you could also make the drawer out of fiberglass as well. Just depends how much your looking to spend & how fancy you want it.
You can buy all the supplies locally to build one yourself, im sure your husband could figure it out. there are alot of tutorials you can read online to help you through it. I work for a company that makes fiberglass spray equipment so if you need resources let me know, Id be glad to help by all means.
How big are you planning on making the drawer?