Adding new Exchange 2013 Server in existing deployment

Hi All

I have one Exchange 2013 RTM (CAS+MBX) server in organization and I wanna get HA by implementing additional Exchange 2013 server and create DAG.

Before installing new Exchange server I have a question about installing version that differ than existing one -can I install Exchange 2013 SP1 as additional server in infrastructure where Exchange 2013 RTM exists?

I imagine the following scenario:

1. install new Exchange 2013 SP1 server near existing Exchange 2013 RTM server
2. move all mailboxes from Exchange 2013 RTM server to Exchange 2013 SP1 server
3. add new server into CAS publishing farm on ARR
4. update or reinstall existing Exchange 2013 RTM to Exchange 2013 SP1
5. create DAG from both servers

Is it correct steps to get desired HA?

Thanks in advance.