Open Source AV Proxies and Network Scanners?

Zphbeeblbrox asks: "Our Company is looking to set up a central proxy/gateway for several of our Networks. We would like to investigate some of the Open Source Antivirus Proxy solutions and AntiViral Network Scanning, however the information we have on them is rather sketchy. Have any of you had experience setting up DansGuardian with the Clam-AV plugin or similar such solutions. Additionally the mail proxy with Clam-AV solutions? If you have, what advice and recommendations would you have for us. Do they work and should we consider using something like snort-inline to scan our network traffic for viruses? I have found little by way of comparisons or reviews on them so I'm hoping you will be able to share some of your experiences on their effectiveness."