Few more comments:
I see you have a SSD as your OS drive. You would benefit from fast I/O operations, if you keep your datasets on SSD. When saving NRRD (or nifti) volumes, Slicer tries to compress files by default. As far as I know, compression is currently single-threaded and can be quite long for large datasets. When you are saving, you can optionally disable compression (expand Options, and uncheck compress). Here is a related post showing the impact compression may have on I/O: Can Slicer utilise multiple cores on linux? - #6 by muratmaga
Your GPU is good that you should get very nice 3D rendering performance in volume rendering. If it stutters, make sure to set the Rendering quality to “Normal” (Advanced->Techniques->Quality in Volume Rendering module).