My favorite part is bass, subwoofers aren't easy, sure, adding a decent subwoofer to a system to supply more bass is no big deal, but getting the best possible sound out of a subwoofer IS.
Now, if one subwoofer is good, are two or more subs even better??
Of course it depends from the car size, type of music, how old you are etc... Anyway, if the car is not in every day use I think more subs are even better.
So here we go, what about 2x15" or 4x12" or 2x18" I'm still not 100% sure, but I have one of my old setup already tested-
and it's this one
P3020367 11-16-00.jpg
another shot
P3020364 11-16-01.jpg
nearly whole setup
P3050377 11-16-00.JPG
Yaeh, I know, question is how to place all of them inside boot. Well I'll manage somehow :-/ For me most interesting are 2x18"- so will take this decision soon