Did a lot of testing and it seems there's some kind of ground loop between the laptop and the AMPs. While running on laptop battery the system has no noise. As soon as the DC charger is plugged the noise starts and fluctuates as the system activity changes. For example the noise changes as the HD activity changes. Moving the cursor around on on the digital fx skin causes the buttons to highlight and you can hear it in the noise. Leaving the charger plugged in and connecting another laptop does not introduce any noise.
This is pretty much the current setup for power:
It seems the noise goes from the charger to the AMPs. The only analog part of the system is between the USB sound card and the AMPs so thats were Im going to do some more testing.
Usually power line filters shield the HeadUnit for example from picking up noise from the alternator. In this case is the "HeadUnit" (laptop + charger) the one introducing the noise. Will installing a power line filter between the laptop charger and the car battery stop the charger from introducing noise to the system?