After a putting a Bazooka CSA8A5A in my old Mustang, I want to put a
subwoofer in my 1999 Lincoln Continental with the factory (non Alpine)
am/fm/cass/changer. The Mustang system uses a 5 channel amp to high
pass and boost the power to the factory speakers, and that works
REALLY well, so I plan to do the same in the Lincoln.

A couple of 2 channel amps under the seats or something seems like a
no brainer for the factory door speakers, but I am not sure at all
what is going to work best for the subwoofer.

Where to mount the subwoofer in the trunk?
There are spots on the rear deck for a pair of 8" subs, and some kind
of grill in the middle as part of the taillight which I have no idea
how is used or could be used.

How would sticking a 10" sub in a box behind the rear seat work out,
ie no new holes etc. If so, has me thinking about just picking up
another CSA8A5A, ie I really don't need a LOT louder system, just some
bass and like 6 more db out the doors (easy with factory speakers if
high passed).