The best place to route wires to under the hood

I'm installing an amp in my 2013 DC and I need to run the power wire to my battery. I wanted to hear some ideas on the best method(s) for getting wires to under the hood. I know that I can go through where the main wiring harness comes in by lifting up the boot and going on the outside of that, but it leaves a slight gap.

 

I installed my amp behind my rear seats, and ran the wire outside of the truck zipped to the frame. There are little rubber knockouts underneath the truck that you can remove, use a screwdriver to poke a hole in, slide the wire through, and reinsert the knockout. Easy makeshift grommet. They are under the carpet in the cab so may be a little hard to reach, I was able to get to the one underneath the front passenger seat without removing anything. Pulled the wire up through there then ran it behind the seats near the door.

Something to consider, just make sure your wire can handle the elements. I tried getting it through where the main wiring harness is and gave up, couldn't get it to sit right, so went with this approach.