How Do You Add An Aftermarket Amplifier To An 07 Es350 W/nav?

[saabkyle04]

I am adding a sub to my car and I am curious on the process that someone would go through to do this. I am going to add a 12" Rockford fosgate sub and a Kenwood amplifier. I am going to fun a remote cable for easy bass adjusting up to the driver's seat. The only problem is I don't know how someone would hook it up to the radio itself. I have the ML system with NAV and all I am doing is adding this sub to it, I'm not changing anything stock whatsoever. how would it work to have it hooked up? Would the volume on the sub be turned up with the radio volume? even though I have the bass remote and controls on the amp itself, will the sub's bass be increased when I increase the Stock system's bass?

What I am trying to say is that I want to control the bass of the stock and the sub separately, (remote vs. controls on the NAV system) but I want the volume of the sub to go up with the radio! Is this possible?

Thanks so much, I really appreciate it if someone can help me with this!