ouch, so you have a single SQL server over the WAN from 6 sites each with their own SEPM?
that doesnt sounds right. you may want to evaluate replication or GUPS for remote sites, depends on how many clients at each site though.
SEPM is a pretty SQL intense app, the recommendation is to have SQL + SEPM on the same switch or at least in the same datacenter. Your SEPMs are sending over every log (av, scan, traffic, packet, etc) from every client for entry into the DB or if there is a console open, the SEPM will be grabbing all the reports and data back to the console through SQL.
With replication this same DB data is sent, but it is compressed and entered all at once on replication. console sessions would not go over the WAN either in a replication scenario, which will improve performance for them considerably.
Did you upgrade from SAV? Topologies that worked well for SAV, don't always carry over to SEP well.