I have 300 connected sites the head office, through VPN. All of the sites use Cisco ASA. And now I need a software to manage all these equipments (monitor and configure). What can use?
You definitely have to look at the CSM for 'management' of 300 ASAs. CiscoWorks does not offer much in terms of day to day management tasks and security policy management (It is not meant for this anyway).
The base product support's 50 devices but CSM can be licensed to support 1000's of devices.