PS - When measuring voltage drop make sure you include the hot and neutral both. Meaning, for a 50’ 12 gauge Romex we expect ~ 3.2V drop per current carrying conductor, of which there are two: Hot and Neutral.
So the total effect of the voltage drop would be 6.4V total dropped (available) at the appliance, a little over 5%.
Assuming linear amps with unregulated supplies:
The lower the AC voltage the longer the recovery time for the amplifier storage capacitors, After an amp has been turned on and warmed up caps will only charge at the peak of the AC waveform so this becomes a bit of self-maintaining situation.
Whether or not it will affect your listening is another subject altogether, but personally I run all my gear after a Furman voltage regulator which keeps the incoming AC within 5 V at any point in time. After my amp has turned on the biggest issues to my AC voltage are my heat pumps, oven and normal hourly variations in power supplied from the transformer. My modest 100WPC integrated just doesn't stress the circuit very much.
Most other audio devices are fully regulated, and, with enough excess storage capacity, may never feel any difference between 100V and 130V.