This is a two year old thread.

You don't have to set the database to single user in order to restore a database. You do have to have exclusive access to the database you're restoring. One way of doing that can be to set the database to single user, although, if another connection is already there, that can cause problems. I generally go for restricted user, but, in this case, the third party apps all need privileged access, so that won't work either. Best approach here is likely just to kill every connection first.