OK, here is what I have and what I'm trying to do...

First off, my goal is to keep the stock HU!!!
I am replacing the front components with Focal Polyglass 6 1/2" components
Keeping stock rear door speakers(running off of factory amp)
Adding one 10" IDQ subwoofer in enclosed box
Would like to run front Focal components and 10" IDQ off of an Xtant A4004(4x100). Rear channel will be bridged for sub.

I have been told by an experienced car audio guy that he could "hack" RCA's into the factory wire harness(at stock HU, before stock amp) instead of running two LOC's. Is this possible? If so, is "hacking" before the factory amp correct, or should it be done after? I'm willing to purchase the LOC's, but he told me it isn't necessary. This is how he added Xtant amp/subs to the existing Bose stereo in his '02 Altima.

Any insight into this process would be greatly appreciated! I trust that this can be done...my only fear is a "noisy" system. This experienced installer also told me that the quality of RCA's would not be important. He gave me two sets of very basic RCA's to install myself. I questioned their quality, but he assured me it wouldn't matter.

I'm really struggling with this. Please help!