One of my clients asked me to check his network. In his server rack I found a Fortinet FortiGate 60 and a Zyxel Zywall 70. Both of them are - in my opinion - complete firewall solutions for SOHOs (which he is with 1 server and about 10 clients).
Since I'm not a network expert, I don't know if this setup can be useful or if it is just redundant.