I hate to chime in - most of you know I did a bit more above and beyond for said "audio" systems - However I wanted to say there is a gromnet in the firewall next to the brake and gas peddle - this is a great place to run 0 gauge so it avoids heat and elements and easy access to the battery under the fuse box and under the windshield wiper fluid port.

However since your using 0 gauge... you can not fit it under the door jam/seal/trim. Now what I did originally was ran it under my center console along the gear shifter and e-brake. The back-end can bow slightly enough so its un-noticeable. then you can run it under the carpet along the "bump" of the frame and you won't know its there.

Or you can notch the plastic/cut holes in the frame.. I mean your choice. just depends if your running 1... 4... or 24 0 gauges (yes my friends 24)...to a copper block in the spare tire well