Looking into this same issue... Found a new system through Infinity called the Basslink T. This is basicly a really shallow box with three ten's and an amp built in. The rep says that it will require a little "reconfiguring" behind the seats, but nothing too drastic. You can check it out at http://www.infinitysystems.com/caraudio/product.aspx?ProdId='BASSLINK+T'&Ser=BSL&Cat=PSU
Ill let you know when I get mine installed.