I've been thinking about this build way too much the past couple days but I think I finally have everything locked down. Since I already purchased the LCQ-1 and 4 Channel Alpine.
With that being said I'm going to have a grand ole time running wires but I think it should be well worth it for all the options I'll have.
I'll be summing the front left and right channel's highs and lows with the LCQ1's summing feature. Unfortunately this only gives me a single Left and Right output but to remedy this I'll just use two RCA splitters allowing me to run identical left signals to both the front and rear and the same for the right.
The sub's connection will then come from the rear mids as documented from the UberStealth install.
I think those may be tuned lower than the fronts anyway? If that's not the case I may just spare myself the trouble of running the wire back there and letting the LCQ get the signal from the front mids.
So now that I have the signals combined I'll be using JL Audio C3-650 Crossovers for the front and C5-650's for the rears. This should give me roughly the same crossover point as the factory's while allowing each set of speaker to receive a full 65w RMS at 4ohms. The crossovers also have the built in tweeter protect for tinkering
The big benefit to this is that I'll have total EQ control of the system through the LCQ-1 as well as retaining the stock speakers/look. Although it's not ideal to have the crossovers in the back of the car I'll be splitting all the wires close to the factory amp. Allows me for easy replugging if I ever need to go back to stock and keeps everything close for wiring.