I'm not sure that two or three corals is the right idea (especially if this means coral frags). To have coral, you'll need different (better, more expensive, brighter) lighting, and the associated algae issues that can come along with that. You'll also need a lot better control over water parameters (test kits, time, a bag or bucket to hold the hair that you pull out). Those things might be more worth it for something closer to a full blown reef tank.
Just thinking about cost-benefit analysis on adding a couple corals vs sticking with fish/inverts only.