Bradish54

I want to add a subwoofer to my 2018 ford fusion, i am going to run a 2 channel amp for the front 2 speakers (6.5 inch kenwoods) 100 RMS, then add another amp for a subwoofer. i have a line out converter to use by NVX (xlca2) similar to the audiocontrol LC2i. my question is would it be okay to tap into the rear deck subwoofers instead of tapping into the rear door speakers? my main goal is to not have to take out the factory stereo. I know the rear deck subwoofers have a amplifier to power them so i wasnt sure if they had a crossover that would mess up signal going to the loc or if it would be okay to tap into those instead of the rear doors. I was going to run 1 power wire to a distribution block to power both amps, then ground both. either the rear door/rear deck subwoofers to the LOC, then also power the loc with its own power wire from the battery or add it to a pre existing fuse. If anybody has used those rear deck subwoofers to run a amp let me know if its possible and how it turned out, if nobody knows then i will just stick with tapping the rear door speakers.