Hi John, It has been a while since I played a KN7000, but I recall, to me the drums were not great (preset), as you described another "boxy" is a good term....I remember Uncle Dave had to use a separate out to eq the drums thru a mixer..
The method you described is one of the things I did like on Yamaha, allowing to use a drum pattern in place of the seq drum track, the down side, I dislike the drums on the Yamaha...
John could you post a demo of your results, or email me a clip...I think I should listen to another's work, and not rely on my memory..