I believe when you click notify on the board it should notify you of any new activity.
If it doesn't try this:
Under account settings, then notifications, Where it says "for topics and board I have requested notification on, notify me of:" And change that to 'replies and moderation'.
I believe that will then send an email telling you every time there is a new topic, and also a reply to that topic. Regardless if you have actually subscribed to it individually.
I will play with it today to be 100% sure.