First of all sorry for jumping ships but this is far more relevant knowledge for HE-6 users.

I have a Hifiman HE-500 that I have been using via the speaker taps of a transformer coupled tube amp (musical paradise mp-301 mk2). I am well aware of the need to use resistors with such tube amps to keep the transformers cool and happy. Based on the parallel resistors equation ( combined resistance = R1xR2 / R1+ R2 ), I have a combined resistance of 5.68 ohms from both my HE-500 resistance of 34.5 ohms (measured) and parallel resistor of 6.8 ohms.

The resistors I am using have a power rating of 10 watts (based on forum recommendations, including Garry the designer of the MP-301). Here is my question: Why does the resistor have to have a 10 watt rating? Can I get away with say a 1 watt resistor (or less)? Would a 1 watt resistor soak up less power leaving more for the headphone? The amp outputs 6.5 watt per channel only so I would like as much of that pumped to the headphone. With a higher output amp this wouldn't be such a concern. Thanks for any input.