On the server you have SSC, you can first install Symantec endpoint protection manager console..these two can co exist.
then create package and push to your sav 10 clients, once 11 is installed , your cleints will now report to symantec protection manager,
once all the migration is done, uninstall ssc, uninstall sav and install sep on the same server...
check these links for more info
https://www-secure.symantec.com/connect/forums/upgrading-symantec-av-corporate-edition-10-sep-11#comment-3387541