Much confusion abounds regarding headphone power requirements.
This RaneNote is intended to disperse some of the mist surrounding headphone specifications and hopefully give you a clearer understanding of how much power is really needed for your application. What they really mean is dB SPL for 1 mW input. For example, if your hi-fi amp is rated at 65 watts, then you would need only 65 mW to drive comparable headphones. And this is exactly what you find in hi-fi receivers. Their headphone jacks typically provide only 10-20 mW of output Power.