2003 Dodge Ram Stereo Wiring

Okay:

Truck:  2003 QC with 6-speakers
Current Unit:  An Alpine in-dash dvd with nav
Facts:  We used a Metra patch cable for the initial install to easily connect the new headunit to the factory harness.

Since replacing our Infininty speakers with the sponsored Polk speakers we have found that they obviously needs more power than the Alpine unit and the factory head unit can supply.  In fact, the loudest of all of the speakers are the three dash speakers while the new door speakers pale in comparison.

As such we have decided to install a new Polk MOMO amp (4-channel).  What we need to know is this:
1)  Should we just disconnect the factory amp and replace it with the new Polk --- and what is the easiest way to do this since this is a 4-channel and there are six factory speakers.

2)  Or, should we just keep the factory amp to drive the dash speakers and then how do we only pick and choose the wires to drive the four door speakers?

WE WANT TO AVOID RUNNING NEW SPEAKER WIRE TO THE ACTUAL DOORS...WE WANT TO TAP/SPLICE THE WIRES BEHIND THE DASH TO MAKE REMOVAL EASIER.

Any help would be appreciated and if you have a make-shift diagram you can email us since it would be easier to understand.

THANKS!!!!!!!

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