I'm planning on getting a 4 ch amp to feed my door speakers. Pioneer 4-ways up front, 3-ways in back. Question is this, should I run new wire to each speaker, or will the stock wiring be enough? I'm looking in the area of 60w x 4.

 

With 60 watts a peice I would upgrade the wire. Go for 16 gauge

 

Run new wires, that way you can make sure everything is phased properly.