You already have that power. However, I have it configured so that you must choose to receive such emails. How you say? Click on the little plus next to "Additional Options..." right after the submission box, and there you'll see more options. Simply mark "Notify me of replies" and you'll receive email notices to replies in said topic. In addition, if you check out your profile, there's an option under "Notifications and email" you'll find you have more options as to how you're notified and when, and whether you should receive such notification emails by default.