I am using a HE400i with a Sonata HD Pro which is enough to drive it more than loud enough with high gain trick, but to really bring out the dynamics out I use the xDuoo MT-602 desktop amp. If you have a budget of only 5k or less, I can recommend the Sonata HD Pro dongle, otherwise please spend the 7.5k on the xDuoo hybrid tube amp at the very least, if not the 900rs Apple USB C to 3.5 dongle as well. Not like the HE400SE will be particularly portable anyway, and you will still be able to get decent volume out of phones and such, but you can't beat the SQ of a proper desktop amp, at least for budget Hifiman planars.
Moreover, once you have a powerful desktop amp, you can upgrade your cans without much hesitation as well.