Well this is one very easy job on the coupe:-
Take a feed from the battery and run it down the passenger side of the car to the boot (where I presume you will be placing the amp.
The route from the engine bay is actually very simple and requires no drilling or cutting.
There is a grommet you can use in this pic:-
Exit engine bay The lead then exits behind the wing. You will need to remove the 2-3 bolts at the top of the wing, (two are hidden by the foam pad). Then very carfuly you can pull away the top half of the wing and see where the wire exits (note the alarm siren in here too)
Behind the wing I would add some heavy duty wire screening to stop the wire chaffing against the enty and exit points too.
Now feed the wire into the B pillar.
To see the exit point you will need to peel back the carpet from around the b pillar, it is easier if you remove the door rubber from this area.
You can see the exit point in this picture:-
Exit point into the cabin Now just run the wire under the carpet down the side of the door and then remove the rear seat cushing to find a hole into the boot. I actually made a separate hole at this point to avoid any interference by running power near phono or speaker wires.
Hope this helps
John