No antivirus or device will stop today's threats. This has been in the news for years and while these devices and protections are pretty good they are not perfect. That is, WE are still the best protection. If you have employees that open every email attachment because they think the antivirus/wall will protect them, they will be infected with something.
I guess the word is naive when folk think there is a perfect solution for Windows platforms.
My employer paid hundreds of dollars for a Sonic Wall and still got a virus. What do you suggest a person do if they pay hundreds and still get viruses?