What is the difference between the Million Color Wheel Well Kit, and the Advanced 3 Million Wheel Well Add-On?

The Million Color Wheel Well kit is available in both a full kit or an 'Add-on'.  The full kit includes a control box, which is capable of powering the Wheel Well Lights only.  The Million Color 'Add-on' kit is meant to be added to an existing Million Color Underbody Lighting Kit (will work with both Standard Million Color Underbody Control Box, or SmartPhone Million Color Underbody Control Box).

The Advanced 3 Million Wheel Well Add-On Kit is meant to be added to an existing Advanced 3 Million Underbody Lighting Kit only.