2002 Chevy Tahoe OEM Stereo Wiring Helpl

As all projects like this seem to get more involved, I decided to swap out the front and rear door speakers as well. The fronts line up properly to the standard GM colors, however both rear doors are BROWN / yellow.  Am I to guess that the rear doors are run in mono? My meter is broken, or else I"d have metered the drivers first, but this sure seems odd. The vehicle also has some smaller round drivers in the C pillars (4x6/3 1/2"???).    Does anyboy have any input or a factory schematic for this? I searched the forums and archives with no luck. 

Also, I have a JL 8IB4 that I was going to toss into the factory sub location for kicks. Presuming that my Alpine deck will interface properly with things has anybody else done this swap? If so, with what results. Yes, I know it won't be like 3, 12W6's, but the factory setup is so sad....

Please drop me a line back with any help, it's all appreciated. Thanks!

they are not wired mono.. that's just a common harness for the doors.. same in both.. use brown for +

and the PAC piece for the On-Star works GREAT! The Soundgate piece, well, is a piece..

The rear is just a little rear fill.. something like a 2 inch or something.. never measured them.. not quite sure.. too small for a 3.5 though.. I usually don't' hook them up when I do a big system.. for a smaller system.. just leave them.. they are more of a tweeter than anything..

replacing with an IB4 will definately improve the sound.. I personally have never put an IB4 in there.. but have the W1 and w0.. with no problem and little modifing..

George, I have both the  front and rear door speakers installed and moved forward to do the head unit swap. However none of the speakers will pop when given signal. Am I wrong in thinking there must be an amplifier somewhere other than in the OEM head unit?? If not, please let me know what I must do. If I have to rewire the doors I will but I'd much rather grab the OEM wires somewhere inside the chassis.  I'm looking to run the head unit to the 4 doors, loose the little 2 1/2" drivers and maintain the OEM sub in the back with an upgraded woofer. Any help?? Thanks.