You will hear all the common names again (and again

), but for what it's worth: look at Symantec Anti-virus corp edition...
Very manageable, you can configure it to be totally silent (i.e. nothing pops-up on your clients, they don't have to do a thing, so they can't do anything wrong).
And the latest version offers the extra of spyware detection, which is the biggest new plague if you ask me.