Ciao Axel,
I just modified my system as following:
SSD is connected to SATA2_0 port
HDD where GPL is saved to SATA2_1 (do you think I should move or fresh install it on the SSD?)
HDD for storing documents, pics, vids to SATA2_2
eSata HDD for storing to SATA2_3
DVD to SATA2_5 (I guess I should set back to IDE this port and SATA2_4 too, see BIOS pic)
both C1E and C&Q are now disabled
Unfortunately, in my BIOS I cannot set the exact RAM voltage as in yours: I can only increase it in +0,05 V step, see BIOS pic
Now it's time for some tests: I'll post the result later.
Again: thanks a lot for your great support and understanding.