The multi-institutional ARIES study is developing several visions of tokamak magnetic-fusion reactors, with varying degrees of extrapolation of physics and technology, to project the economic, safety, and environmental features of future fusion power plants and assess their competitiveness. A comprehensive systems and trade study has been conducted as an integral and ongoing part of the reactor assessment in order to identify acceptable design points to be subjected to detailed analysis and integration. Results of these systems studies are summarized; some of these results are interim.