I was in your shoes, or boots a couple of years ago. I had the heal rub issue with my Kenetreks, and had to make a change. I now own 3 pair of Crispi boots, and wont look back. I have the Bridsdal, Thor and Pro Light GTX.
The Briksdal's would be like the Kenetreks regarding the stiffness, but dont feel like a ski boot, and the lace to the toe system is amazing, the Thor's are very light and comfy, but still offer the needed support, and the Pro Light GTX are in the middle of the Thor and Briksdal as far as stiffness. I dont have heal issues with any of the 3, or issues with the balls of my feet like I had with the Kenetrek.