I've had the privilege of meeting Jeremiah Grossman at a security conference. I'd recommend reading several of his white papers and then decide if you want to call his company up. I doubt they are cheap, but the best rarely is.
Does it not seem odd to you that the only competitor for Windows file sharing recommended here is a open source clone of the same technology they are trying to replace?
There is a reason why Windows servers are so popular and it is no one makes directory services, file sharing, group policy, and email/calendaring as easy as Microsoft. Microsoft has been so successful at creating these services and making them simple to administer that most open source projects try to emulate/replicate/duplicate what already has been done.
So stay up on your soap box saying how much better the open source version is...
Scientists will study your brain to learn more about your distant cousin, Man.