2001 Toyota Sequoia Limited Edition w/JBL System

Hello everybody. I have a Sequoia with broken factory radio. Recently I bought a new aftermarket radio/navigation unit, which I'd like to install. So far, I've got everything working besides speakers. The car has JBL system with factory AMP. The radio wiring harness's audio wires are in bundle of seven thin wires (black, red, white, blue, yellow, green, brown) and one thick wire (black). I have been playing with these wires, and cannot figure out, which is a set of positive/negative for front and rear speakers. I've been looking for some info, and the one found does not seem to be for this Limited Edition, and appears to have different wire coloring or setup. Anyone would help with this problem? Thanks

Not sure if it applies to your situation but I recently did an 03 Highlander with the jbl system and went to the passenger side rear/cargo area underneath all of the carpeted trim and plastic compartments there I found the factory jbl amp, got my amp turn on there and speakers wires.  They make something called speed wire that I recommend if you have to run from the deck to the factory amp like that.  All speaker wires and amp turn on wire loomed into one.  Makes life alot easier.  I think the amp turn on was pink if I recall correctly. 

The AMP in Sequoia is behind the radio. Also, there has to be a way to use factory radio harness, because Crutchfield.com sells an adaptor, that plugs into original connector. Some people say, it works fine with this model of Seqouia. It probably would be much easier to buy this adaptor, but I already hardwired all other wires from the new radio to the harness.