You can use the variable MS_REF_MASTERFILELAST_DESIGN = 1 to set default update sequence so that the active model updates last which means it will lie on top of the attached references.
Note that this variable needs to be set before the model is created. It plays no role when dealing with existing models.
Suggested workflow: Set MS_REF_MASTERFILELAST_DESIGN = 1 and create a new design model. When references are attached, they will be drawn first on the screen followed by the active model. You can use the keyin expand set MS_REF_MASTERFILELAST_DESIGN = 1 to set the variable as a temporary variable for your current design session. Refer to the following for more information: http://communities.bentley.com/communities/other_communities/askinga/w/askinga/set-temporary-variables-with-the-expand-set-keyin.aspx
Snipped from Help: Determines the default update sequence of references and master model for Design Models. This configuration variable is used at the time of creating a new model to set its default update sequence. If 1, references are drawn first, then the master design model