hooking up an extra amp to factory bose system

Hey, just got a quick question thought id check in here and see if any one could help me out. I have an 03 silverado with the factory bose system and im adding in another amp and subs, got the line converter just not sure which wires to grab the signal off of to run my rca's, if anyones done it sucsessfully and wants to let me know where they tapped in id appreciate it...thanks

Brian

first you need to locate the factory amp becasue you will have to get the signal after the amp. then find the outputs and tap into the rear speaker wires

actually i ended up finding a pin out of the connector at the back of the H/U...tapping in after the amp gave me shitty sound quality but i grabbed the speaker wires at the back of the head unit hooked it up and sounds great....thank for the reply though