Here are some updates since I made this topic.
Here is a picture of the 4 gauge wire for the subwoofer amplifier going through the firewall.
Here's the awesome Street Wires cable I got for the speaker wire. It's 8 wires (2 per speaker) and a remote lead all neatly wrapped in a nice thick jacket. 20 feet of it for $30.
And here's the heat shrinked and soldered joins to the wiring harness. I just plug the harness into the dash, plug the wires into the amp and I'm done.
I've also got an air ride suspension coming which has its own screen I will put on the visor, and I'm looking at a unit called Connect2Car as well.