line out convertor

Hello, I need some help! How do I install a line out convert to an already amplified system? I have a 2006 Chevy Impala LTZ w/ Bose System. I am wanting to add 2 12" subs (maybe some 15s") Alpine Type S and a 1000w RMS amplifier to this vehicle for added bass. YES, I am a bass junkie! I love the clarity that the Bose System has but looking for that extra something. I am wanting to retain the Factory head unit because of the 6 disc changer and didn't want to go through the process of buying extra parts to retain the On-Star, Bluetooth, Chime, etc. I usually would take out the factory but since its Bose, and those other reasons, I'd rather not. I found the PAC AOEM-GM1416A but its recommended for 2007 & up and the AOEM-GM1416 isn't compatible with an amplified system. Here is what I've done already: I've run the 4 gauge power wire on the passenger side from battery (fused) to trunk. I have the remote wire running along the same side from a wire I spliced (Using a T-Tap connector) to amp. Amp is grounded, but what do i do with the RCA Jacks and which L.O.C. do I us. Any help is appreciated! How do I install a line out convert to an already amplified system?

I would consider finding a speaker that has already had the high frequency filtered out of it. tag that to get signal.Hutson-