Question and Answer Page

I am looking for some advice on the best way to achieve this:

I want a page on my main site where registered members (paid not free) can ask a question and certain members (experts level) can only answer them. However all members free included can view this page.

I have looked for plugins, have looked at using a forum for this, but none (from what I could tell) have the permission levels for starting a thread or posting. The closest I have found is a theme that does this, however it comes with a price tag that is too much to test if it works.

I have seen a very rough and not very good free q&a theme in the WordPress repository.

Any ideas?