How do you set your Main Volume level for going directly into the PA Mixer (Output set to Master Stereo) ?
In the beginning about 2 years ago I thaught to have distortion in clean rigs on my in-ears, thats why I turned the main volume to - 20 dB
and it worked.
But I think the sound over the PA could be a bit better and would like to hear your suggestions for dialing the right main volume. 
I think the main volume dont change the sound, its only the volume. So it doesnt matter if its on -20 or higher.
I find that -10 going to FOH keeps most soundmen happy it also shouldn't contribute to any distortion in the sound unless the FOH desk is clipping and sending distortion back to your monitor mix
In my experience some soundmen already complain at -10 dB, so I give them -15. 
The Kemper comes from the factory with all outputs connected to the Volume knob.
But, in the Output Section, you can connect your choice of Outputs to the Volume knob.
I have the Monitor Output controlled by the Volume knob, and use it to control my stage volume. The Main Outputs are not connected to the Volume knob, and are set at -15db or -20db (depending on the sound tech's preference).
However - Turning the volume down to -20 does not change the quality of the sound - it simply reduces the volume. The best sound for a guitar through the PA is interdependent with the sounds of all the other instruments, and not what we usually like to hear onstage (and not like a personal in-ears mix). So... get it to sound as great to you as possible onstage/in ears, and you will play your best, and that will make more of a difference to the audience than any small tweaks in the Mains.
Thanks folks for your answers.
I remembered to have always heared that the signal should be as high as possible (of course without any clipping) rather than to amplify it again in a following stage.
Think I will ask the technician to try with -15 dB while it works for Ingolf ... 
I've had issues with distortion through avioms distorting. Happens with hot signals. Depends on the signal flow of the board. Sending the house a weaker signal helps. Using a Yamaha digital board, the input trim didn't affect aviom levels, so apparently the aviom sends were before the boards preamp. One sound man at my old church finally figured how to adjust them
