just box, amp, and subs will do the job.
things you need, and can get pretty much anywhere, but a local best buy would be a one stop shop.
1) sub of your choice (I reccomend a alpine type-r 12", really clean bass)
2) box you can go ported or sealed (I recomend the q-logic single 12" ported/sealed box w/ 1.125 cubic foot of airspace)
3) line output converter (all this does is take speaker inputs and turn them into rca outputs for getting signal to the amp)
4) amp wiring kit (you can use 8 awg kits, but 4 awg would have more room for upgrading later.)
5) positive battery terminal
6) and of course amp of your choice (I recommend the alpine mrp-m450 400 watt amp)
-steven-
