[Mike P.]

If you want to keep the cost down, then use a 6 inch diameter piece of sonotube for the port. Use a router and a round over bit to "flare" the end. A cheap way to line the sub is to use egg crate foam from WalMart. They sell it as mattress pads for about 15 dollars. There should be enough in a "twin size" to line the walls. The Acousta-Stuf you linked to is for stuffing a sealed sub or for adding to a ported sub to make the box seem bigger to the woofer, which you don't need to do.