replacing factory amped 3 way components

tried searching a couple key words but didnt find anything relevant. i imagine many similar questions have been asked before but hard to find i guess. anywho, i'd like to know what you guys think would be the best way to go about this since there are several ways i could do it. ill list the components i have at my disposal for this project below. the vehicle is a 2010 Lexus RX450h standard audio w/ factory nav. the front doors have factory amplified and crossed over 3 ways. the tweet(capped) and mid are fed by one signal from the amp and the door woofer is fed separately by the amp. the rear doors are two way components fed by one line from the amp. the sub is dual 2 ohm i believe. i have two sets of rockford fosgate T165-S 2 way components with bi-amp capable passive crossovers im planning to install in the front and rear. also installing a alpine pdx-4.100 amp and a pdx-1.600. i have an audio control LC8i to use as an active line level converter and it's capable of channel summing so i can construct a full signal to feed the front doors (if you think that would be the best route) heres what i want to know. what do you think would be the best way to set this up? 1. Nix the factory mid? and use the lc8i to build a full signal which will be amplified then split at the crossover and feed the new 2-way components? 2.keep the factory mid? fed by the factory amp then use the lc8i to sum the high and low signals from the factory amp to feed the aftermarket 4ch and send a full signal to the passive crossover in the door which will drive the aftermarket tweeter and woofer while the mid remains powered by the factory amp? 3. something else?

If you are installing the new front speakers then ALL of the factory front speakers should be removed for best sound quality.

You should simply think of the tweeter, mid and woofer as an inseperable unit which you will be removing an replacing with the RF unit.

Best results will come from supplying the RF unit with as clean and unmodified full signal as possible(use the audio control) and use the x-over on the p4.100 to high pass them.

Are you going to use the stock subwoofer with the p1.600? ... in any case the x-over on that should be set to low pass the sub at the same frequency as the high pass x-over on the p4.100. 

Dodge Magnum in progress:

Pioneer DEH-80PRS - PPI Amps - Dayton Subwoofer(s) - Exodus Anarchy's - Vifa Tweeters - Kinetik Battery