Hello all, I am very new to the high-end end audiophile market so any help from you experienced members is greatly appreciated. My current cans are Sennheiser Momentums, which I have had for ~2 years and absolutely love. However, I've decided its time I step up my game so I've ordered a pair of Sennheiser HD650's that are supposed to arrive tomorrow. My Momentum's only have an impedance of 18ohms, but the HD650's take 300ohms. I primarily power my headphones from my Retina MacBook Pro or iPhone 6 and I've heard to get the most out of the 650's an amp is a must have. I've also read that they're notoriously hard to power, being a novice to all of this I'm sort of overwhelmed and confused. I currently own a Fiio E6 (it was like $28), which claims it can power 160-300ohms. Will these do the job or do I need to buy some more gear? Also what are DACs, and are they worth the money? If it is going to cost me another $200-300 to power these headphones I will just return them and wait. Thank you very much!