Renewal subscription

Hi,

I'm going through the process of renewing all of our Fortigate FW support.  I'm trying to understand these different kind of subscriptions that I have to renew.  The vendor suggested that I should purchase Advanced Malware Protection, NGFW, Web Filtering, and AntiSpam.  Of course, I also have to purchase, Enhanced Support, Telephone Support, HW, and Fireware & General Updates.  It sounds like I have to have the second 4.. that I know.  The question is the first 4 of them.  What do I need to purchase Advanced Malware Protection if I already have an AV system within our network?  Same thing for AntiSpam if I already have a dedicated Spam filter service, etc...  Thanks in advance.