What kind of subwoofer should I use for my car {10 pts!}?

8 inch subs will do the trick for tight, accurate sound. The design of the enclosure, including the cubic volume, size and depth of port, and amount of stuffing are critical elements to your sound quality. 10 inch subs will produce slightly more, slightly lower b at the expense of a small amount of clarity for more bang for your buck. I think you should consult one to three of your local audio shops for some good advice, good options and some demo's. Stay away from cheapie chains like Best Buy, etc.