Quote (Avoid @ Feb 22 2012 10:48pm)
Depends how much room you want to take up, aka if you wanna take up the whole back seat, under the seat, or behind the seats.
Might just wanna stick to some shallow mount speakers like Rockford Fosgate P3-S, 10's or 12's.
I'd recommend Level 2 8's or Sundown 8's or the Sundown Shallow Mount 10's, not a big fan of rockford. But your budget will decide what you end up with, if you need everything for cheap then you might have to resort to the rockfords it all depends on how you want to run it and how loud you want to be and your budget.
If you go sealed you save space and gain SQ but sacrafice SPL. If you go ported you're more limited on where you can put the subwoofers and the type/amount you can use but you will yield better SPL. If you want something seriously loud and don't have a low budget and don't care about space go with 2 ported 12's or 15's. It's all variable.