So I'm all of three weeks into owning a 2007 MCS and consumed with learning everything I cam about this car. I am attempting to upgrade the HU with a Pioneer AVH-X2700BS, but am confused about why some keep and hide the old unit behind the speedo? Also, using an adaptor harness, I can't get the new unit to power up. Maybe I'm missing something here. All fuses are good, the HU works, but not in this car. My MC has the base audio system with six speakers, if that helps. I appreciate any help/advice you can give