Hi, how would you classify Pocket Amp2 More Information About The Portable Headphone Amplifier high voltage low current or low voltage high current. is it more suitable for driving low impedance headphone or high impedance headphones...

I have read many threads on this forum pertaining to impedance. but i dont understand one thing. there are some famous brands like grado and denon that have quite expensive low impedance headphones. what is the advantage of having low impedance on headphones.