Stories for subscribers only

I'm planning to use antville as a blogging system for my company. Is there a way I can set it up so that any stories posted to the site are only available for subscribers? Making a site public seems to be opening it up to anyone who visits the site, while keeping it private means only the author can read it. Isn't there a "public for subscribers only" option?

Also, is there a way to allow users only from a certain domain to register? In other words, can I set it up so that only people from my company can register?