Got to thinking. I have been on Head-fi since 2004 and heard my fair share of amps/headphones. I have been laptop only for years now and recently the headphone jack died. I picked up a Dragonfly v1.2 which sounds amazing considering it is only $150. However it doesn't quite have enough power to full drive my Sennheiser HD580s(650 drivers in the mail yay!). It sounds good and far better then a normal headphone jack yes but at higher volumes you can just tell it isn't getting enough power and really needs a dedicated amp(I ordered an Asgard 2 yesterday since my Little Dot is getting stale). So why did Sennheiser make them 300 ohms? Couldn't their engineers make them 120-150 ohm? I still own a pair of Sennheiser 590s and the Dragonfly powers them very well, I believe they are 120 ohm but don't quote me on that. So is there anything in the 580/600/650 driver design that requires them to be 300 ohms? Thanks.