2dee11 
Hey you can get a cheap harness for like $30 but you will loose your door chimes. I routed my 1/0 gauge wire though the firewall on the driver-side there is a rubber grommet plugging up a hole nothing is running through it. I just used a utility knife and cut a x into it ran it though there. Yes I know the car is very dirty. After it gets in the car it just runs along the floor under the back seat and into the trunk. I will eventually run it under the carpet all the way to the trunk.
This shows it running across the firewall it used to be tied up nice and neat but since the car is not running atm I uncliped to work on some stuff
Here is how I got it routed behind my fuel lines and down beside the break booster
The blue wire is my power for the amp it runs down underneath the brake booster I couldnt get a good pic of the grommit but it is right by there it is easy to find by feeling
Here is where it comes into the car right next to the steering collum
The peace pulled down is the carpet
I just cut a hole in the carpet to run the wire though so it would not interfere with the gas peddle
