Appropriate Norton Product?

I work in a 12 person firm with a very old copy of Symantec Anti Virus Server ver 8.00.9374(2002).  Recently viruses have been getting past the Symantec Product even though it still distributes updated virus definitions on a regular basis.  My question is, what is the appropriate package or group of packages for a firm of this size.  We are running Windows XP throughout except for our file server which is running XP.  The Symantec currently is loaded on its own XP server.