For the next drop, in testing with several headphones now. I would say if your headphones are over 50 ohm I would get something with more power. My Sennheiser 518 are the highest impedence headphones these gave any impact with. Even an 80ohm set is pushing on these giving you and noticible benefit. Then again for a portable amplifier, I am not sure how many headphones are meant to be used with this, most portable headphones are 32ohm or less, which this will most definitely give you a noticible boost for.