Well, i don't know about antivirus software for companies but i run a network and i use panda titanium antivirus, its free and it comes with a small firewall.
here at philips medical systems, we use VirusScan Enterprise 7.0 by mcafee, upgrading to 8.0 this week. I don't know how much the licensing is, but it might be worth a look.
I have been selling and installing Norman Antivirus for some time now, and I have to say they are by far the best for Home, Business, or Enterprise. The software has this technology they like to call sandbox that finds viruses that have not been discovered yet. All my clients love it and the price is much lower then Symantec. Plus you dont have to worry about a virus infecting you Anti-virus rendering it useless, like you do with Symantec.