I found one with a lower crime rate than Kennesaw and it's in godfry's stomping grounds,
West Linn, Oregon which has a crime index of 120 and roughly 20,000 population right on the outskirts of Portland.
Edit: West Linn has a median of $72K per household, Kennesaw, a relatively high $60K. Hmmm, rich suburbs have lower crime. Go figure.