As someone who doesn't check their email much, having notifications pop up on-screen (similar to how Facebook notifies you of a new message) when someone comments on one of your posts would be uber helpful.
There's no popups option with this forum software for reply notifications, that I can see. You can set it so you get a popup notification of new private messages.
There, it will show you all topics you were "subscribed" to (i.e. ones you would have had emails about). The icons to the left of each of the listed topics should indicate whether there are unread (by you) posts on that topic.