Installing After Amplifier

[Ricksinfinit]

I’m new to the group and new to Infiniti’s but I just picked up a 2007 M35 with the basic no frills system and I am definitely researching a upgrade. I just got the PA15-NIS IPOD interface which makes things tolerable but I am, by no means going to settle for the current system the way it is. I also just downloaded the service manual and being an electronics engineer by trade, I’ve been going over the AV Systems schematics. I want to add a four channel amp and I was wondering if anyone else had done so where in the system, did you install it and where did you physically mount it. Thanks