Need help choosing a CMS system

I need a php CMS system where
1) users can create other users and the creator can assign private content and file sharing permissions to their users. the requirement is that i am providing a file sharing service to companies and they should be able to create their own users and the content is shared between that group.
2) optionally the content (discussions, files) should be hidden from other groups unless allowed by admin for that group. I realize it may not be possible for all of these features to be available in one cms but 1 is a good starting point. I believe a multi site like wp mu will be an overkill.
Can anybody suggest the closest to out of box solution for this.
thanks

 

Actually, Joomla can do this for you and right out of the box too.

Unless I'm mistaken, but can anyone else confirm this as well?

 

Joomla can do most things that you might want indeed.

That almost sounds like a social mod where you can create "interest groups" and either allow it to be private or public.
Don Luttrull

 

joomla is the best CMS as per your requirement .. u can add, delete,disable .whatever u want in joomla ..

may b this will help check it out http://docs.joomla.org/Adding_a_new_user

 

Visit http://php.opensourcecms.com/, you can find the demo of all the CMS available and their features. Try the demo and choose the CMS you want...!

 

Lanius CMS...

See it in use on my first sig link...

You can create "Subsites" which will allow the creator to have there own network of users. Also a handy downloads manager and more...