I would appreciate advice or suggestions regarding which Wiki is most appropriate for a technology transfer program for a company with approximately 300 employees in six different offices.

The primary requirements of the program include:
1. Store, organize and share information (Word, PDF's, Spreadsheets, CAD Files) between employees and offices.
2. Messageboards or forums for usergroups within the company.  Ability to notify all members of a usergroup when new messages are posted is desired.
3. Establish company "yellow pages" with searchable database of projects, clients, employees and technical documents.
4. Ability for employees to upload information.
5. Needs to be simple to navigate.


Thanks.