I get involved with a lot of people's box designs and I've come up with a box that absolutely pounds AND sounds great. Build a 2.5 cubic foot enclosure with one 4" inside diameter vent that's 15" long. The box doesn't need any fill or insulation lining the walls. Just make sure you use 3/4" MDF or thicker material and put in a couple of braces to help stiffen the box up. One thing that's popular is to use a second piece of 3/4" on the baffle board. This second piece has a hole in it that fits around the speaker's basket. This acts to recess the speaker 3/4". The extra thickness of the baffle board will help kill some of it's vibration. Use one of the yellow colored woodworker's glues and either screws or air nails. Paint the interior of the box with a water based sealant. One of the cheapest and easiest is called snow coat. It's made for roofs. It's white and kinda chalky when it dries. This stuff will seal the MDF (it's not as solid as many people think). Just remember, the best woofer in the world will sound like crap if the box is crap and a low buck  basic speaker will easily out perform it in a great box.