I will cut all the stock speaker wires at the head unit and run them (probably via 9 conductor speed wire) down the drivers side. Wire up the amp to the battery and ground there in the trunk, along with the remote connection at the backup sensor pig tail. For sub signal, I'll get it from the stock amp wires that are back there. Then, run those wires to the sub. Lastly, run speaker wires around the side of the car and up into each door and the dash tweeters.
Supposedly, the JL 500/5 has switches for high/low inputs, so I can probably splice in an RCA connector to each speaker wire instead of using a line-out converter. Or, I could buy a 4-channel LOC and be done with it (probably easier than splicing 8 RCA connectors). Get a 4-guage power kit for the amp, 25+ feet of 9-conductor speed wire, and 100 feet of 14-gauge speaker wire, and probably a few odds-and-ends connectors.
That should be about it, right? Am I missing anything essential?