I intentionally decided not to, "cheat," and install the cable the OEM way. Once I figured it out, the OEM install took about a half hour. Also, I've heard about the foam, but decided not to do it yet. But after hearing it and discovering how easy it is to remove the box, I might add it in the very near future.
To future readers:
When you begin to run the cable along the sill, start by pushing it directly down right next to the foam and before the hole the carpeted trim piece uses. Push it to the sill and pull it out there. Then reroute it again all the way along the sill. Next pull the carpet on the front side (hood) next to the door out a little but. You need to pull the carpet loop off of the plastic tab to do this. Then gently pull the carpet back. You will see the plastic sill will end and you can reach in a grab the cable as your pushing it. Once it is out of the sill, you can route it up the footwell and then across to the radio. make sure to use the zip ties to secure it properly. It will make some more sense once you have pulled the sill off and see it. Hope this helps!