On the 03-up models, you can go to the brown accessory wire coming off the ignition harness, but you won't retain the RAP feature for the amp. To keep the RAP feature so your amp stays on with the radio when you turn the key off, you wire a relay so that it triggers from the RAP supply voltage wire from the BCM. But if you don't care about listening to the radio much once you turn off the ignition via RAP, then attaching the amp's remote turn-on wire to the brown acc wire would be the easiest solution.
