I have an 01 LS430 w/ Navi . I am trying to connect my 2 subs and 4 speakers to an aftermarket 5 channel amp while still using the stock head unit. I have already found the wiring diagram for my car. My question is

1. Do I use a 4 channel line output converter for the speakers inside and then get another 2 channel line output converter for the subs or will (1) 4 channel line output converter be enough.
2. Where would I install the line output converter? Does it go close to the amp or does it need to be behind the head unit?
3. Should I rewire the speakers to the amp, or just connect the old wires that were going to the stock amp?

 

1. Get one for the subs. Audiolink makes some good ones. Not cheap though.

2&3. Line out converter taps the signal from the stock amp. Then feed the signal output to the aftermarket amp. Aftermarket amp to the speakers. Install in a place which would be conveinent for you!