So, what we see here is a low Power DSP with limited number of taps and some sophisticated measurement technique (pls. correct me if I wrong)

Hanatsu, can you please clarify some points:
1. Do I need to measure Power response in full sphere around the headrest or, for example, in some plane with center at the headrest? Will changing measurement points field alter my results?

2. Windowed measurements in the Car are almost useless, and with 200 ms window I don't really see how it can be different from simple pink noise "moving mic" technique

3. What about FR in the listening point using good old REW with single point or averaged? Is it comparable to what you were able to achieve before?

4. FIR filters are great for managing phase. Can you control phase with this device? Are implemented filters minimum phase or linear phase? Square wave response plots would be great to see.

5. Open source FIR filter-generation tools are well developed and tested. What exactly separates APL from them (except hardware, obviously)?