Moving a Debian Setup

If you can get a trusted network, a combination of netcat and tar is probably the quickest. See for example Dan Walronds guide.

Use rsync to copy the contents of the current machine to the new machine.

It would be much easier if you used a configuration manager software, such as puppet or cfengine. Ideally, if you had done it before, you would just have to reapply the same classes to the new server and let it deploy your configuration, but you could still do it now, describing your current configuration with puppet and applying it to the current server to check that it works fine, and then applying it to the new server. This will allow you to cleanly duplicate the server whenever you change again.