I drive a 2011 VW GTI with the premium Dynaudio sound system. I am keeping the stock amplifier and speakers and only swapping out the head unit.
Here is what I have used.
Pioneer AVIC-X940BT
PAC RP4-VW11
Ground Loop isolators
ENFIG AAA-VWAUD5 (Don't actually have this yet, waiting for it in the mail)
Parking brake bypass via an additional wire inserted above the mute wire. This wire and the parking brake wire are both grounded.
From the headunit I have used the speaker level outputs with ground loop isolators wired in.
I added in the ground loop isolators because I had a white n
