single domain scenario

we wish to implement a single-domain network structure for our company. We

have 45 remote branches all have an average of 20 users per site and have

300 user's in HO. Since we have a server on each branch that host some

applications, we intend to make this servers a DC with AD integrated DNS

for the local users be authenticated locally. Some links / websites

recommend to put a Global Catalog on each site to facilitate the logon query

locally but i have also read about implementing a universal group membership

caching w/c they said to be ideal for remote branches with limited bandwidth

and harware resources. I've got confuse on this part on which to place with

our DC on each branch ( GC or the group caching setup ). please shed some

light on me. Thanks