I have a 2005 Roadster. After talking with three different installers at three different shops, all are in agreement that there is just no room for a sub box in this car. There is a tiny bit of room in the trunk, but the top folds down in there and the fuel tank is between the trunk and the passenger compartment. There are two tiny spots behind the seats where the factory pseudo subs go with the factory infinity system, but the seat backs are tight against these spots and they are too shallow to hold any real sub.

So, the plan is to just go for a single set of components in the doors with plenty of power to them and hope for the best.

Head Unit: Blaupunkt Hamburg MP68
Components: Crossfire X6
Amp: Crossfire XP6004 bridged.

There is a slight possibility of fitting some 6.5" components behind the seats, but the installer thinks running more power to the X6's in the doors would be just as beneficial as using the other two channels for those.

I am open to opinions, the install is scheduled but I can still change my mind