I ran my 1/0 cable down the wheelhouse (or whatever you prefer to call it) to the frame, and then along the frame rail next to the fuel line to the back of the car where I put it through the floorpan via a grommet. Where it passed near the engine and exhaust I ran it through some heat resistant cloth like what you'd use on spark plug wires/boots.
Since the 1/0 gauge is fairly stiff, I found it much easier to run this way than trying to conceal it under the carpet and make the tight bends that'd required. Plus, it eliminates any EMI issues that may arise from running the power cable near the interconnects or speaker wiring. Plus, should it ever need to be upsized (however unlikely) I can do so without pulling any of the interior - only the floor of the trunk will need to be removed.