My SC is parked at my mom's, otherwise I'd take a look and see how I'd do it.
I used to have a 1977 cutlass, and what I did on that was ran it between the fender and the firewall, then into the little rubber boot that covers the wiring between interior and the door, then into the car by your feet. I don't know if that'll work on a unibody vehicle though...
Also, I've heard it's better to run the power cable on the side of the vehicle opposite the RCA/speaker wires, due to noise problems.