amping the interior speakers in 99 yukon

hey guys, i'm new to this board & i figured it wouldnt hurt to ask you guys how the heck to get the rear door speakers to work?? i'm installing pretty much a full sound system in my friends 99 yukon... pioneer 8600 deck, MTX 564 (4ch amp), rockford 1001bd (mono amp - sub), 4-6 1/2 inifity reference components (front & rear doors) & 12" kicker l7. anyhow, i finally got everything in... but i ran the wires per my friends request. he wanted the wires for the four speakers (only the ones in the doors), run to the back of the head unit & tap into the speakers from there to save me the trouble of running all new wires to the speakers. so i went ahead & did it this way but, now only the speakers in the front doors & the ones in the way rear (4x10's - stock, but wont be used at all... or so the plan is) only work. will i have to run new wires to the speakers in the rear doors for them to function or where can i tap into the stock wiring for these rear door speakers to work?? anybody have a wiring diagram for this vehicle?? also, i thought i'd mention when i removed the rear speakers, it seemed that both the rear door speakers appeared to share one of the same color wires while the other two were different colors (make sense??). any help would be greatly appreciated -gsus

All makes sense. The rear door speakers run off a factory amp. Easy way around it is to take off the door pillars and access the wires there. They will match the colors you found on the rear door speakers.

^^^ thanks, i dont know why i didnt think of that, i was dreading the thought of having to run new wires through the boot in the door!