Hi Kenz,
IMO, they more suitable for full size cans. The International is like The National but with a bit refinement and added more power into it. In my experience, driving IEMs or let say medium size cans with a lower impedance (such as z1000, momentum, Grados), the sound is fine, but i felt like is not proper enough, especially in the bass department (too many energy) and the sound is like too big of what the lower impedance headphones can handle. But i am not too sure whether is caused by that 22ohm or else.
But when i use it as a dac to my laptop (only laptop+international), I found the sound is noticeable different. Not by much, but seems like the power was tamed a bit, the bass was more controlled and the sound was a bit cleaner to my ears (compared to if i used it with setup like IPC+CLASdb+International as an amp).