Sharon - Sorry to hear about your experience with corn in the Champion. When I was looking for an electric flour mill, I borrowed a flour grinding attachment and it was clear to me even grinding wheat was hard on it.
I paid $175 for my Vital Mill electric flour grinder. I only use it for wheat, barley, triticale and rye. I tried buckwheat once and it was clearly putting too much pressure on the mill. I use my Corona hand grinder for buckwheat and will also use it for coarse ground corn meal. (I have been working on some flour corn varieties for this part of the country but haven't tried grinding it for polenta yet.)