This digest shows the design process and optimization results of a highly compact 3 kW, 12 V server power supply. In the course of a comprehensive analysis of the key performance parameters of GaN e-mode HEMTs compared to their Si Superjunction counterparts, the most suitable topologies and control methods for the PFC and the DC/DC converter stages are derived. In a subsequent step, the system is fully optimized with respect to efficiency and power density by means of multi-objective Pareto-optimization. Based on the results, the design parameters of a system with a power density of 80 W/in³ and a peak efficiency of 96.4% are presented.