2006 gmc sierra bose system

I have a 2006 GMC sierra and it has the Bose stereo system. It doesn't have the subwoofer under the cup holder in the center console. I want to add a subwoofer and amp that I have using my stock stereo. I have a line out converter so I can hook up my amp. My question is where is the best spot to tap in line out converter? I used to hook them up right behind head unit. But I heard that with Bose system its better to tap in to the wires under center console. Are the rear channels wires light blue and blue, and yellow and brown?Are those the same color wires im looking for under the console? Also do some the trucks with the Bose systems come with and without subwoofers? And the Bose sub is under the cup holder right? Any help is appreciated.

hey, i have just been looking into the same thing with my luxury bose system on my 2009 sierra denali, for me i can hook right into my sub wires under the cup holder but if you dont have the stock subwoofer you will have to tie into the rear or front speakers. and from what i have read into some people say after the amp some say before. there is alot of people talking about it if you google it.