Antivirus for Exchange 2007

Which of the following corporate AV solution is compatible and the best for an Exchange 2007 server?

1. Sophos
2. Panda Business Secure 2008
3. TrendMicro OfficeScan 8.0

I’m currently evaluating these three options proposed by different vendors. Based on Gartner’s “Magic Quadrant for Endpoint Protection Platform” report published in Dec 2007, Sophos seems to be a good alternative to resource-hogging symantec, but I need to know from your experience.

Hope to hear from you guys soon!

Thanks.