Roundcube Plugins (on postfix - dovecot - Centos 6.2)

I have setup Roundcube and a password plugin. This works fine.

Now I wanted to install forward / vacation and a calendar plugin for Roundcube. But here I see that most of these plugins require LDAP. Can somenone write his/her experiencie on setting up Roundcube to work with LDAP. And is it better to do so. Or am i wrong on this?

I have also installed via the installscripts Horde, but I think that by following just the install script I am missing a great deal of Horde, because there is no LDAP server running.

Is this correct and would that mean that the best thing for me to do is to start setting up a LDAP-server.? I have read on this forum an in the manuals about LDAP and it seems hard to maintain the users in LDAP on Virtualmin. Or is this just a feeling because I am not familiar with LDAP.

I hope you can point me in the right directions and give me a good general view on how to install a good Roundcube setup with forward / vacation / calendar and password.