Any suggestions on the best way to setup our SEP11 infrastructure?

Have 24 sites with about 500 clients at each site.  2 Servers including SQL at each site.  We have a district office with about 130 servers and about 200 clients.

I was thinking of having a primary SEPM at District and maybe a 2nd SEPM for fail over with SQL DB on a SQL 2005 Server.  Then either have a SEPM at each site with an internal db or just a Group Updater???

Any ideas at what would be better and easier to manage?

Thanks,

Kris