Without paying too much attention to the unknown issue for me beginner, I ended up buying 8 ohms speaker set for my Zone 1 (JMLab Cobalt 816 series) and 6 ohms speakers for my zone 3 (Dali Ikon 6).

Receiver (Yamaha RX-V2600) was set to 8 ohms at the beginning, but after I purchased Dali speakes, had to set to 6 ohms. I kind of feel that Cobalt speakers sounded better when amp was set to 8 ohms, but I can't use it now... as impendance is set as global parameter for the receiver.

What can I do in this situation without actually changing speakers, which I like...