Good point, i should have mentioned that about possible hum issues, the 120r resistors do indeed muddy the presentation, but its easily solved with a couple of resistors in the heater supply instead.
I never had any issues with the volume control range, on the 4ohm tap anywhere from 1/3rd to 1/2 volume is the normal range i use, which is roughly the same as a HD650 running on the 8ohm tap.
If you ever want to test the background noise levels for yourself i found the Crackheadphone is slightly more sensitive than the Grados, i.e. when using the stock cable without the resistors.