Dear Pander, as you guessed making a minimal example and further reading fontspec manual helped, though without the hints from this list I would not have found out which problem to fight in the first place. It turns out one of the things I tested (AutoFakeBold) was what was needed. I just did not see the difference between normal and bold text because with the default setting this difference is rather weak with this font. I had to use much bigger value.
So, with this list's kind help, I finally got what I needed. Thanks a lot to all of you, Susan -------------------------------------------------- Subscriptions, Archive, and List information, etc.: http://tug.org/mailman/listinfo/xetex