[A380Driver]

The front amps might also be different than the rear amps (I havent looked) but up front you have tweeters too...so I know it splits the signal. What happens is when you turn on the headunit, it sends a "turn-on" signal to the amps which then allow them to draw power and in turn, power the speakers. This "turn-on" feature is so the amps will not be drawing power when the headunit is off. What may be happening is the headunit is not sending that turn-on signal to the front amps, and therefore, you arent hearing anything. It may be because of a faulty headunit...maybe a loose connection in the back of the headunit.

The best suggestion is to work the problem from the cheapest solution, to more expensive and up...hence check those connections to everything first.