Recently I have been introduced to a new modeling tool called Enterprise Architect.
It is truly a great product for a great price.
It has full support for UML 2.1.
They have a robust and easy solution for distributed teams that have a need to access design artifacts.
Local File or Shared Network Store
As with any modeling software you can store a file containing your models.
You can easily configure SQL server to be your backend store, which allows a multi-user access to your modeling projects.
Either you can use a DBMS in conjuction with a Version Control Product (Shared Model)
use a local file based solution with a Version Control.
The major source control providers are supported out of the box, and you can add support for work item tracking in tfs with an optional plugin.
The price is very reasonable at $250 for an enterprise seat.
Compared with $5000 for Rational Software Architect, which is comparable to Power Designer and ErWin.
If you want to do some serious modeling without having to sacrifice your yearly budget. I would suggest getting a few copies of enterprise architect for your team.