The 750 Watt power supply would be more than enough for this task. The PowerSpec PSU is an 80+ Bronze, which would give you 85% efficiency at 50% usage. https://en.wikipedia.org/wiki/80_Plus
I'd strongly recommend using MSI Afterburner or a similar program to reduce the power consumption of your GPU.
Submit photos and a description of your PC to our build showcase
See other custom PC builds and get some ideas for what can be done
Services starting at $149.99