HiPwr HU to factory amp'd speakers

Im hoping someone can help with this.  As a gift, Im giving an aftermarket head unit for a '91 Mercedes 300SEL.  Does anyone know:

1.  Does this model have amplified speakers?  If so:

2.  I was told that you can wire a hi-power head unit with only the + leads to the speakers only to avoid overpowering factory speaker amps??  Is this possible?  If so:

3.  Please send wiring diagram for '91 300SEL. 

I found some answers.  Some models are amplified, some arent.

If it is factory amp'd - the amps to the left/right side speakers are located in the trunk respectively.  The front speakers are also powered from the trunk amps.

Im told the HU hi-power input will not damage the factory amps.  Would like to find a diagram now, probably only available from the dealer.