Ok, thanks! I did not understand that those settings are so critical, I thought that they are just for fine tuning...

Anyway, with options following options I was getting something like 700kh/s per GPU:

  --scrypt -I 20 -g 1 -w 512 --thread-concurrency 24550 --gpu-powertune 20

But then in a minute or few, temperature of the GPU´s rise to somewhere near 95c, and then whole Windows crashed with a blue screen :-o

What would be maximum temperature for such Radeon cards??