This guy John with A.I.S. Audio Integration Solutions (A.I.S.-Audio Integration Solutions <
1pocket73@sbcglobal.net>) made a harness for me on my 2019 Silverado and he's about to make one for my 2024 I have now. It taps in and gives you a signal for all channels, but also gives you wires that keep you from needing to rewire the truck, all plug an play. Excellent work he does. Hope it helps those not wanting to tap into the speakers manually and cut anything, since it's all plug and play. See the video below.
Also, thanks for all this...I'm ordering the same 6x9s and rear door speakers today, and just reusing the 10" Infinity Kappa sub I have in the SubThump box I had made a few years ago. SubThump had a single 10" box that I had him adjust to be the same size as the dual 10" box that filled the entire underseat area, but the speaker box was only on the passenger side, and the drivers side and center are just storage, so I don't lose my underseat storage. There's enough room for an amp, tow rope, lug removal stuff, and a truck gun.
Question here, did you sum the output from the door and the dash, then feed it to the amp, then the crossover and from the crossover back to the door and dash locations? Because the outputs are separate and not full range. Just trying to make sure I get the full signal. I'm thinking I'll just go with the tweeter in the dash instead of adding the 203S, might lose a little mid, but most of that is coming from the door anyway, and I can avoid putting a speaker in the A-pillar. Thoughts?