big- yah, the basslink. i've used both bazooka and basslinks in past cars and i have to say the basslink is far better than the bazooka.
it's not so much the pre-fab itself that's the problem (well, in bazooka's case you cant do too much with it since they do suck as far as attack).
it's usually placement, user eq contouring, and the ability to know wat to do with the sound when it sounds a certain way. most folks just put something together and place the sub whereever is most convenient. it shakes the car so it must sound good.... nope.
also professional audio sometimes use plastic cases for PA speakers. ive done projects with well known professional audio pa systems in the past running $1K+ 15" and 18" driver units (retails are $3K+ for one box). they won several awards with that system long time ago. major recording artists used their speakers for major events. they use like 50 of them to power their concerts.
the funny is that i was the one that handcarried the housing on the plane from one country to the next during its initial development. it was a huge plastic box and customs were confused wth i was carrying.
i told them it was a playhouse for a cat.
most speakers use MDF. my studio monitors in my music room are MDF.