syncing user accounts?

Hi,

I administer a small network of 15 Winboxes and a Linux server, which
does all imported stuff (samba, mail, ldap,...). Now I have a second
Linux machine and would like to have identical user databases
(/etc/passwd and /etc/group) or better central authentication. My
final goal ist to authenticate against the LDAP server. But I believe
I still need a sync'ed passwd on every linux box?

I read about NIS but it does not seem to be the best choice concerning
security, is it? I also dont like like the idea of RPCs. I found also
an alternative in kerberos, but it sounds complicated and oversized to
me.

As you see I am pretty confused about the whole process of
authenticating and authorizing users.
So, what is an up-to-date and secure technique to have centralized
user database? What do you use?
Or please point me to good information about that topic. Googling
around without having an idea what to look for is hard.

Thank you,

Tobias