i know many say that you can run these off your phone but my hd600s sound horrible on my note 4. Even using an o2 or magni 2 uber i feel subjectively they could sound way better. i would consider personally matching them with a bigger amp like an nfb11, jotunheim, rnhp, deckard..... as at least the starting point for these. understand b4 you buy that these have a signature sound that isn't for everybody. be sure because it sucks buying some phones and hating the way they sound. these are a bargain but only if you love the hd650 sound. if u have a store that will let you demo different brands and types that might help you make up ur mind. i personally find the 650s too dark for my tastes. You might consider the he400i still on sale i think. the kickstarter ora graphene close backs. monoprice m1060s for 300.00 i think.
Yes, they are 300 ohm headphones, and as such they are hard to drive. The sound signature is a relaxed treble for easy, non-fatiguing, listening for hours. There is no perfect headphone. Most people have several pairs for different moods and types of music.