DXOMark gives the following scores for ISO:
G16: 230
RX100-2: 483
Nikon Df: 3279
If you need low ISO capability, the newer full frame cameras are so much better-- you can’t really beat a Full frame + f/1.8 lens unless you violate the laws of optics. Even a f/0.9 lens will only get you two stops over a f1.8.
