I have a few customers that use ESet NOD32 for servers and workstations, and swear by it. I have also never had a server or WS compromised using the full version of AVG. I don't have a lot of confidence in Kaspersky, Mcafee, or Symantec.
http://www.eset.com/us/business/
The strength of ESet NOD32 is its minimal impact on the OS/memory, and that it gently pushes users to install Windows security updates in a timely manner.