To improve the efficiency of advanced power systems, Integrated Computational Materials Engineering (ICME) tools are being developed at QuesTek Innovations LLC for the design of high-performance alloys for gas turbine. In this work, we detail progress on the design of a low-Re, highly-castable, creep-resistant single-crystal Ni-based superalloy (QTSX). CALPHAD-based indicators for castability and creep resistance as well as many other design criteria were simultaneously employed to predict an optimum alloy composition. Component-level QTSX trail castings have been fabricated and characterization of the castings has demonstrated freckle-free solidification and creep resistance comparable to CMSX4 and ReneN5, validating this accelerated ICME approach. The accelerated development greatly speedy up the qualification process using the modelling results as guidance for targeted experiments, which paves way for higher TRL and great potential for commercialization.