DO not install SEP client on SAV server as it iwll un-install SAV server.
Till you have SSC installed SEP CLIENT cannot be installed.
Once you Deploy SEP on a SAV client it automatically removes SAV and Installs SEP..however if it is feasible for you to go with uninstall the SAV client, reboot, install the SEP client
you can do that as it will be a clean install.
Let your SAV server manage SAV clients.Install SEP MANAGER on the SAV Server or any server and start deploying clients except on the server.
Once all your SAV clients are migrated to SEP then
Uninstall SSC, SAV server reboot and then install SEP client on the server.
You can have SSC,SAV, SEP Manager on single server
However you cannot have SSC with SEP client or SAV with SEP client together.