Hi, I am installing a 15" sub in my 83 733i. I have one problem: I cannot find a way to get wires to the trunk. I have to put RCA cables and a power line to the amp (which then goes to the sub) but there does not seem to be a hole in the backseat to the trunk.. Under the rear speakers, there is a metal plate. I am not sure how thick it is and if i can drill directly through it to go to the trunk. Has anyone else had this problem or know a solution? Can I get to the truck from behind the rear seats? Also, which would be the nearest power supply to the amp, the one from the rear speakers?