Yes to be clear, the D1 are incredibly easy to drive, like almost all dynamic moving coil headphones. It’s because the efficiency is a sky high 100 dB from only 1 milli-Watt of power (and this is quite typical for dynamic coils). It doesn’t matter that 32 ohms is low impedance, when so little actual current is required to drive them to ear shattering levels. 32 ohms would draw a lot of current only if it was less than 80 dB sensitivity. And that’s where the planar-dynamic headphones (HifiMan, Audeze, etc) come in the conversation, with powerful amps (like small speaker amps) required. Those headphones are typically ~ 50 ohms with MUCH lower sensitivities.
Even though D1’s are super easy to drive, you’ll still hear them sound different from OTL tube amps (warmer, bassier) because of their high output impedance.
Dynamics headphones are so efficient because they can pile a lot of coil turns into a very small space. The downside of this is that they have MUCH more moving mass, and the diaphragms are necessarily much smaller. I mostly stopped listening to dynamics after starting with electrostatics. Dynamics tend to give me listening fatigue, even if this doesn’t show up in measurements. Maybe it has something to do with those fat coils and thick, low area diaphragms slapping around right atop your ears.