I have always had a problem with playing whilst monitoring the "recorded" cab sound, with all modellers etc, and the same with the KPA. The sound is excellent, but I just cannot get on with it as I need the "amp in the room" sound when I'm playing.
But now of course, that's all changed. I use the monitor out with cab off into an FET amp into a real guitar cab and listen to the "real" guitar amp in the room, but I record the sound from the KPA main outs. Happy at last. :)...... and I also sometimes record the dry direct guitar sound too just in case I want to re-amp later.