Sealed Boxes that are build to Spec from Medium density fiberboard are the best sound quality. Quality means the ability to reproduce sound as it is recorded on the cd. However Ported Boxes that are tuned to the optimal frequency for the subwoofer are MUCH louder than their sealed counterparts. Take in mind however that a Ported box tends to be around 2.5 times as large as sealed. Bandpass is a retarded idea that makes it almost impossible to build the box to spec tune to the subwoofer so STAY AWAY FROM BANDPASS. Bandpass mostly "looks cool" however isnt a very good performer.