What are you trying to accomplish by having a "staging" ePO environment? Are you planning to manage a separate class of infrastructure that necessitates the delineation between ePO servers? Your agents can't talk to multiple servers, so if you're looking to have a mechanism for testing, then I would suggest re-evaluating, as ePO is incredibly flexible with how you can manage different classifications of devices and products and policies.
The client is a large organization that requires all changes to be staged in a separate environment where other business units can test the effect on their applications/ I know this can all be acomplished using the functions of ePO but that is currently not an option for us.
Probably easiest solution is to follow the Restore procedure in the Install Guide for ePO 5.3; run the Disaster Recovery Snapshot task on your source server, copy the database to staging, then run the ePO setup and use the "Restore ePO from an existing database snapshot"
You will need to download your products again if you need the Master Repository working, but otherwise I think all the client tasks and policies will be available immediately.