fiberglass will give you more options as to what your needs are for the rear storage area. Personally I am in love with JL and will forever be a JL customer. There products last, sound awesome, and are some of the cleanest bass I have heard. I have (4) 12W7's on my garage floor atm, and in the process of fitting 2 in the Z. (Way over powered, but hey I do it cuz I can :P). But remember, your sub is only as clear as your amp. A good amp is important in sound quality. I pushed my W7's in previous cars with MTX 81000 D class amps. So when getting system costs, remember to get a good amp, not just a high powered one. OH, IMO get separate amps for your sub and componets.