TRP - where you are ending up with your car stereo overhaul and where I intend to take mine are moving closer and closer together.
My Boxster lacks door speakers so I’m looking at just overhauling the dash speakers plus the speakers present in the BOSE 986 subwoofer unit. All with a digital signal processor and an active crossover setup.
Looking at your amp installation, I’m considering a similar approach of using the factory CD changer and amp brackets to mount the aftermarket pieces. I’m planning on installing two amps as well (one to drive the front stage and the tweeters in the rear and the other to just drive the 5.25” “subwoofers”).
I too plan on swapping in the Morel CAW 538s as well. There are no 4 ohm versions of these out there so you’re best off wiring these two woofers in parallel for a 4 ohm and 300w RMS.
You might want to swap out that second AudioControl ACM 1.300 for a ACM 2.300. The 2.300 is the same size, can provide the required 300w RMS at 4 ohm when in a bridged configuration (the 1.300 only provides 175w RMS @ 4 ohms).
As for the lack of sound at 100 Hz, both the 1.300 and 2.300 can deliver full spectrum (20 Hz - 20 kHz) and the CAW 538 can perform from 35 to 3,500 Hz so you should be able to get the sound that you desire out of your existing setup. It may be that your cross over points in your DSP are off?
Also adding some of this to the inside of the rear woofer chambers might help improve performance at lower frequencies:
https://www.parts-express.com/acousta-stuf-polyfill-1-lb-bag-speaker-cabinet-sound-damping-material--260-317
Sent from my iPhone using Tapatalk