Grand Prix Sub, Bose Factory System

i've got an 02 grand prix with a bose system (8 speaker, 2 factory amps). i was PLANNNNING on leaving the factory system in and just adding a sub and amp, since i didnt want to bother with the steering wheel controls and on star etc... but it's giving me a run for my money now to the point where if i can't get any good suggestions on here i might for the first time in my life have a shop install it for me!! :( anyway, the problem i'm running in to here is this... there is a factory amp for the rear speakers. in the rear, i have 2 6x9s and 2 5 1/4s. the wire thats feeding the 6x9s is obviously equalized from the amp, and they only put out bass. the 5 1/4s are carrying the mids and highs. so the first thing i tried was basicly just taking the wires that went to the 6x9s and using them as my high level inputs on my kicker amp. well it worked, sort of, but it wasnt right. i could tell the bass wasnt hitting properly, and the subs were cutting out as soon as the volume went even remotely high. so next thing i tried was using the lines that fed the 5 1/4s, assuming maybe the cross over to the 6x9s was a little wonky. well it didnt work at all, i got a very very small amount of sound out of the subs, but zero bass. so assuming the factory amp had some crazy cross over happening, i pulled out the head unit and went direct from the rear speaker outputs behind the HU (before the signal hit the factory amps) - this did nothing for me also. so now i'm leaving with an itch that just needs to be scratched and i dont know what to try next. i was thinking about a line converter, but it's pointless, my amp has a built in line converter. any suggestions???!!! the amp im using is a kicker 650.1

most likely the outputs behind the factory radio are low level outputs. If you hooked these up to the high level inputs on your amp, you would get a very low signal. You could try wiring RCA's directly to those outputs, then going to the RCA inputs on your new amp, that's worked in the pastLife moves pretty fast; if you don't stop and look around once in a while; you could miss it.

i talked to an installer at one of the local shops - and explained my predicament to him. first thing we did was made sure the inputs on my amp were working properly. we were able to rule this out. next, he suggested i try 1 of 3 things. 1 - i ran high level inputs to the amp from the rear factory subs - cutting in to the wires before, and after the factory amp. there was sound, but the amp was clipping as soon as there was any volume. this is obviosuly because i was feeding an already amplified signal to the amp. his suggestion to fix this was to run it the same way, but to add 200 ohm ceramic resistors between the factory amp and input of the after market amp. i havent done this yet. does anyone think it would work or can elaborate on this theory? 2 - use a line level converter and run RCA inputs instead of high level. so i grabed a periphel SVEN4 line level converter, and wiring from behind the HU (before the factory amp), and also in the rear AFTER the factory amp. i got ZERO sound using the line converter. 3 - rip the whole damn thing out and replace the HU, components and amps. we dont want to go there... yet. i like the first one, it seems the most logical. but... i know nothing about resistors. so, how would i mcguyver that contraption? thanks

ok i picked up a different line converter today, and it worked. i have.... you guessed it, another problem now. i have the line converter wired to the factory sub outputs, after the factory amp. the after market amp is getting a good signal from this, there doesnt seem to be any problems with the cross over. when the car is OFF and the ignition is on, it works perfectly (except for the damn dimming lights that we'll deal with later) but when the car is RUNNING, with the volume turned completely down, there is a constant humm comming thru the subs. is there problems with the ground? do i need to ground the line converter? the line converter instructions said for cars with a common ground, to only wire the positve to the speaker output and the negative to ground instead of the negative speaker output. is that my problem? i was hesitant on trying it...