I had a custom one built by a reputable sound shop for my alpine swr 1222D, they asked me what sound i wanted and got the specs on the sub (air space... etc) for their computer program, and then built it out of 3/4" or 1" mdf I cant remember. The box has a tuned port. and sounds awesome. I have a Soundstream xta 360.2, yes only a 360 watts, and it hits 133.3 db with the amp bass boost at 3/4 of max, so if that says anything. if you want pics ill try to post them. OHH YEAH!!!!! ONLY 75$ (plus uncle sams fee) I highly reccomend a custom box ported for your sound preference, i.e loudest possible or best overall coverage of the frequency band, I chose best sound because i like to hear all the bass as close to the same db as possible not just 33Hz or some other arbitrary peak. But if you want competition level bass db then go for it. Hope this rant helps.
Peace
