just get a prefab ported box it will be twice as loud as what you have now, no need to spend extra money on a custom box unless ur planning on ditching those woofers and getting a good amp, but considering this is your first stereo, you will be plenty happy with a ported prefab. and its not cotton its polyester foam. like the stuff they put in pillows. and its purpose is to trick the woofer into thinking its in a bigger box, this is mostly used in small sealed boxes were space is an issue.