Measure the Kix cereal into a large bowl. Measure 3 cups powdered sugar into a large clean paper grocery bag.
Measure the peanut butter, white chocolate, and cinnamon in a microwave safe bowl. Microwave in one minute increments, stirring in between, until the chocolate melts and the mixture in smooth.
Pour the peanut butter mixture over the Kix and stir to coat each piece thoroughly.
Dump the Kix mixture into the powdered sugar bag. Fold the top down a couple times and shake vigorously to break up the clumps and allow the powdered sugar to coat each piece. Add another cup of sugar if needed.
Lay the mix out on a cookie sheet to dry. Mix in the M&Ms, then store in an airtight container until ready to serve.