"Outlaw RR2150. Because when I put 160 watts and .01 ohms resistance into an ohms/volts/watts calculator I get 126 volts; that's without any "inline resistor" defined as resistor placed in series in the line leading from the amps speaker output to the scope's probe. Of course, with the 4 ohm load resistor, the volts come down to ~25."
You do not understand the power specification for the amplifier. If the specification is valid (and there is a long history of manufacturers lying and exaggerating the power), it means that the amplifier will deliver 160 W mean power into a 4 ohm load. That usually means that it will only deliver 80 W mean power into an 8 ohm load (same voltage, lower current). These amplifiers are virtually always "constant voltage" sources, so that the output voltage is a weak function of the load resistance, over a reasonable range of voltage (not a dead short. Therefore, the amplifier will try to put 25 V rms across your dead short, but the current limit (or smoke) will kick in first at the huge current of 25 V into an almost dead short. Also, if you were to dissipate 160 W in a 0.01 ohm resistor, that would be only 1.265 V rms, not 126. You should always check the order of magnitude before trusting a detailed computation.