Simplifying my site - Do I need forum, event calendar, and directory extensions?

I experimented with a number of different extensions and have made quite a complicated mess. I now find myself forced to rebuild my site from the ground up. I am beginning with Joomla 3.1, and CBpro (professional).

Question 1: Do I need Kunena?
Does the Kunena forum do anything that cannot be accomplished with GroupJive?

Question 2: Do I need a separate event calendar component? I was using Eventix, and would consider Ohana for the Joomla! 3.1 installation. But is that necessary? Can the same be accomplished within Community Builder?

Question 3: Do I need SobiPro?
For a global school directory with 1500 listings in 90 countries, SobiPro works well, and provides a handy map module for easy searching. Does such potential exist within Community Builder?

Question 1: Do I need Kunena?
Does the Kunena forum do anything that cannot be accomplished with GroupJive?

They're two completely separate things with two completely separate goals in mind. They're not even comparable. They can also be used together. So whether you need it or not is up to you.

Question 2: Do I need a separate event calendar component? I was using Eventix, and would consider Ohana for the Joomla! 3.1 installation. But is that necessary? Can the same be accomplished within Community Builder?

The only Event based features CB has is GJ Events for GJ Groups, but they're a very basic usage and no where as powerful as an extension designed for Events. So again, whether you need it or not is up to you.

Question 3: Do I need SobiPro?
For a global school directory with 1500 listings in 90 countries, SobiPro works well, and provides a handy map module for easy searching. Does such potential exist within Community Builder?

No, CB is not designed to be a directory extension.