Im also looking for a 2070 Super, and im also returning my 5700XT for the exact same reason. Constant black screens and i have tried everything, i even bought a new PSU, swapped ram, swapped PCIE slots, re-fitted all cables nothing works. The AMD forum is filled with complaints about the black screen of death so i dont feel that confident getting another one the only thing that worked for me was switching the 5700XT with my older card rx480 and no more black screens! Now im looking for a nVidia card because im tired of AMDs horrible drivers.