Theme can use some work and 4 admins for the amount of activity you have (which isn't much at all?) is a bit overkill. No offense intended just my two cents at first glance of your forum.
Would be a wise choice to list some of those things. "You'll be able to discuss things" does not tell me anything at all, every forum is made primarily for discussion.
What can we find on your site that we can't find on others?
* By the way, this is just my piece of advice, nothing personal here.