HA! I had probably the same Koss cans. We're talking 1975 or so. I always assumed that the splitting headache was from the Zeppelin I was cranking into my ears!
@soix , it'll be mostly be an iPhone > amp/dac > headphones. So an amp/dac combo. He's got a Bluesound streamer at home but at school it's his phone.
I've always had headphones (Sennheisers and Grados) but I've never had much luck with amps, though it's been many years since I put my mind to one. I've listened to the AudioQuest Dragonfly, the red I think, and I just couldn't hear much difference from my phone or preamp, but that really may just be me. (See above, re Zeppelin/Koss; my hearing is not aces any more!)