Need advice on a Double Din HU. Looking really hard at the Kenwood DDX8019, but I also have eyes on the AVIC-D3 and Z2. NAV is a must and I realize I need to get the KNA-G510 for the Kenwood unit. Which HU do you guys think would be best for SQ and playing Mp3s from DVD? Any thoughts on the Pioneer Navigation in comparison to the Kenwood/Garmin Navigation?