The problem is that pre Windows 2008 R2, you cannot configure audit subcategories via group policy. You must either stick with the legacy categories or you can configure computers one at a time with by running the local auditpol command.
With Win2008 R2 you get the ability to configure auditing at the subcat level with group policy. All you have to do is edit any existing group policy object in a Win2003 domain from a Win2008 R2 computer and you will see the new policies. They won't impact existing 2003 computers which keep reading the old settings in group polcy and the domain does not need to be upgraded or functionality level changed.