Nice work so far. Lots of work done. I highly recommend either of these amps with DSP for your set up. Best value out there to make what you are doing pay off. They are the same amp so get the best deal. You can cut the speaker wire coming out of your factory amp and just run those 4 channels in to the input of this amp/DSP. Then from 4 of the outputs of this amp connect those back to the wires you cut. You plug your laptop into this amp via usb and you can configure the frequency very easily and get a full signal to each of your new speakers including the rear speakers. Currently your rear doors get virtually no signal. Since you have 2 ways you can send a full signal over the factory wires to make your system sound great plus way more power.
I used this and ran all new speaker wire to my doors and tweeters. I have the AT4X so separate speakers and used all 8 channels. You said you would go to separate tweeters in the future so you could add this now to get a full signal to your newly added speakers then if you add tweeters you can just adjust the frequency and send the correct signal to all of them. For $390 buck this will totally change your current set up and work for future upgrades. Check out my build posts if you’re interested. Did infinity components all the way around at 3 ohms for 50 watts per channel and this JBL amp, then separate kicker key loc amp with DSP for the sub. Also replaced all dash speakers but did not amp so I could blend the door speakers and get rid of the dash heavy set up. You have done the hard work, but getting the right signal to your new set up is the next step if you want to go farther. TheShark and I are just offering help because this system is kind of complicated but fixable. I spent a ton of time testing output and frequently of each factory speaker to completely rebuild mine and get the sound I wanted.
