Hi, after testing and researching a bit more I want to share my findings:
BI-AMPING
There is really no conclusion but try it out and test. A reasonable option of bi-amping seems to be to increase the quality of the (single) speaker cables and replace the jumpers between the binding posts with a piece of the same better speaker cable.
LFE/LFE+MAIN
As said above in this thread, the LARGE setting wit LFE+MAIN leads to weird (not more) bass behaviour. But even though that about 90% of the articles I read recommend the setting SMALL/LFE, there is a small fraction advising the opposite: B&W support (Germany) and Hifiklubben (Norwegian Denon/ B&W-support) would «definitively always set the CM8 to LARGE (with LFE+MAIN)»
LFE and speaker to SMALL with a crossover at 60 / 80 Hz is the way to go for me.
AUDYSSEY/DYNAMIC EQ/DYNAMIC VOLMUME
I was in general too uncritical to the measurements Audyssey takes, and there was quite a process to get that right. Eg. I used the measured setting on all sources and contents (yeah, I know!). Besides, I noticed that the Audyssey App and the AVR take different measures, especially on subwoofer level (+0,5 App, -2,0 AVR).
Now I adjust the settings accordingly. For movies Dynamic EQ and Dynamic Volume is a must because of the low listening levels we tend to watch movies at. Without Dynamic EQ the sound gets really flat, and Dynamic Volume rescues us from continuously adjusting the volume (loud explosions vs low voices). This is more a compromise I had to make - I rather tend to be a purist.
For Music I tested a bit more and there I ended up doing the opposite, especially after I had watched the video posted below. Yes, there is a setup without Audyssey! Music I usually listen at quite high volume and I found it best to completely turn off all available features (Audio Restorer, Audyssey w DynEQ and DynVol) and manually adjust the sound to my liking - using the Graphic EQ of my Denon AVR. This provides a lot more flexibility to get it «right»
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Thanks again