It sounds like you were able to move the server by "replicating" it.
If that is the case, then to move the clients over the best would be to assign them a new Mangement Server List Policy that points to the new SEPM server. Then, keep the old one running as long as you can to make sure all the clients switch over to the new SEPM server.
Oh, by the way, the best is to set the policy on the new server and then launch a replication to replicate the policy in.
Another thing you can do to save Disk Space is reduce the number of Live Updates the server remembers. Live Updates can take gigabytes of space! I'm not near a server (other wise I would be tempted to post a screen shot), but the setting is under Admin --> Servers --> (Click on the local site) --> Site Properties.