Hey mate,
I’ve had this setup in my car for about 2 years now.
2 gauge wire from battery
Then using cable ties
Run your wire next to the fuel filter and down the fuel line. (Fuel line doesn't get hot, so don’t worry about that.)
When u follow the fuel line down, under your back seat (Driver Side) is a rubber grommet, make a hole in the rubber grommet so that the wire can come into the car.
Then you can feed the wire to the amp which is in the back??
hope that helps...
PS. If u want pics, let me know.