Make sure to check with your state insurance commission. Insurance laws differ from state to state, but most state commissions will be able to tell you whether the organization is licensed to sell insurance and whether there have been any complaints about or regulatory actions against the organization.
State regulations keep commissions for insurance brokers at the same rate, so you won't find much variation in the cost of acquiring insurance for your company. So because the prices for all insurance brokers are essentially the same, you can choose a broker based on service.