Installing system in my 2008 f150
Put the amp on the rear wall behind the backseat. Power wire: you can either run it through the grommet near the battery into the cab and run it down the door sill, or you can do like I did and run it through electrical conduit underneath the truck and have it enter the cab near the rear wall.
Some people HAVE mounted it under the back seat, but I don't recommend it. I think it gets better airflow behind the seat and is protected more from feet, etc anything I might put in the back. Mounting it behind the backseat isn't that bad. Check the audio section of this forum. There are some GREAT builds.

