I am looking to upgrade the Head Unit in my 2005 ES330 with Nav and Mark Levinson. Looking at a Pioneer AVIC-8200nex. Stopped by my local audio store today and they indicated that they would need to replace the ML amp as it needs a digital signal from the HU to turn on. Is this really an issue or are they just trying to sell me a new amp? Has anyone upgraded their HU and retained the ML amp? Any issues? The store was pushing the Metro kit to interface with the controls. How does this compare to the IDataLink line.

Thanks