In this paper we study the problem of achieving regulated output synchronization in a network of minimum-phase SISO agents. Our problem formulation is characterized by the combination of three different challenges: the network is heterogeneous (meaning that the agents are governed by non-identical models); the agents are non-introspective (meaning that they do not have access to information about their own state or output); and the agents are not allowed to exchange internal controller states via the network. To handle these challenges, we present an observer-based control methodology that combines elements of low-gain and high-gain design techniques.