As the number and power density of servers within today's data centers continues to increase, efficient power delivery is becoming a major industry concern. This paper proposes a series-connected power distribution architecture for data center server clusters, which decouples conversion losses from the total power delivered - allowing for conversion losses to remain relatively fixed, even as server power requirements increase. Voltage regulation of the servers within the cluster is achieved by the use of differential power processing hardware. This work also provides an experimental comparison between the fully-operational series-connected cluster implementation and the best-in-class commercial power distribution hardware - showing more than a five times reduction in conversion losses. The measured system-level efficiency for a best-in-class conventional power delivery architecture was 97.5%, and the measured system efficiency of the proposed architecture was 99.5%.