So, it is raining but I have been out and changed the switch on the Vibe back to "High" level inputs. The noise and ALL interference is now gone.
I will have to re-setup the gain, crossovers, etc now BUT it seems that I have a conclusion:
The Vibe Litebox only supports balanced differential inputs when configured to use "High" level inputs through the switch on it's underside.
If it is set to "Low" it expects normal RCA inputs with only a ground on the shield, not the reverse of the signal. . . . . . So, you then get a ground loop which picks up noise / interference from the ignition, electric water pump, xenons and other items from the car.