I am a firewall guy by profession for 12 years and have managed various networks from small to enterprise. With a 70 people, I can recommend two fws , choose the one which fits you.
1. Cisco PIX or ASA - This fw requires an experienced guy to manage as someone said, CCNP or CCSP. However this is the fw with minimum issues.
2. Checkpoint - So simple, that even you can manage it ( I assume you are a business person) after reading its manual carefully.
I personally prefer Checkpoint over CISCO for firewalls as the basic fundamental rule for security for me is..
"Security is Simplicity"