This paper discusses voltage gain extension intended for the galvanically isolated impedance-source DC-DC converters under the principle of combined energy transfer when the energy is transferred from the primary to the secondary side using an isolation transformer and a coupled inductor of the impedance-source network. Different realization approaches of the combined energy transfer are evaluated; the main emphasis is on the power conversion efficiency and realization complexity. Also, the application of topology morphing control to the galvanically isolated impedance-source DC-DC converters with combined energy transfer is analyzed. An experimental prototype rated for 100 W was used to validate all the findings.