Hey, I wonder if anyone can help. I'm looking for a CMS that will allow me to do a couple of things. I have some specific requirements but loosely I'm looking for something that will:

1) all users to submit quizes with multiple choice answers
2) allow users to answer quizes created by others
3) award points for actions like creating, answering and getting questions right
4) allow users to spend on-site points for things (such as being allowed to retake a quiz or customizing their profile)
5) Be themeable (allow me to create the front-end code to my design)

I'd be looing for a cheap option and am ok using open source solutions with plugins.

Does anyone have any recommendations?

Joomla!

Wordpress

Drupal

Thanks very much