3 sites - 3 SEP servers, but only one manangement server

Hey

We are using Symantec Endpoint Protection 12 in 3 different sites.

Site1 = 150 clients
Site2 = 300 clients
Site3 = 50 clients.

At the moment we have a SEP management server in each site, that have almost identical setup. The reason for the almost is because people dont always rememeber to update their site with the new settings that is being decided.

We would like to have ONE management point, so the configuration only needs to be done ONCE and not 3 times... But we would still like to have updates locally at each site, to prevent the 150 clients to download from site2 everytime there is a new update.

How can we achive that ?