Not really portable as a headphone amp/dac, but sounds really nice. Btw does anyone else who has the One notice a springy "boing2" sound when when pressing the clickwheel? Is it normal or is it just mine?

They sound super with the fiio X3! Wished the momentum was more portable, now I'm always carrying a man-bag with me everywhere, just so I could bring the case with me. Nevertheless, the momentums really hit the spot for me as far as portables go. Thank you sennheiser! :D