As for the driver: that depends on what you are looking for, i. e. at home / studio use, mobile etc. If you have high-end headphones, you probably also want a high-end DAC / amp.

For desktop use, the Chord Mojo 2 is great, but that's a $650 investment, and probably not matched with the (still excellent) Beyerdynamic headphones (in terms of what I'd expect people to invest if they're looking at those headphones).

A portable option (nothing stops you from using it at home though) that also includes Bluetooth (naturally, with LDAC) is the Qudelix 5K, which comes at around $100 and sounds excellent (even better if you fiddle with the EQ in their really decent app).

The higher impedance in itself means nothing at first, apart from the fact that you need more power to drive it. However, if your equipment is well matched, you typically get less distortion at higher volume levels and better treatment of frequencies, i. e. more clarity and better reproduction.

If you find your equipment can't really drive the higher impedance headphones and you're not willing to shell out additional funds, the low(er) impedance versions are still great headphones.

250ohm isn't louder.

This is my understanding. Audiophiles love to shroud things in mystery. And it's been decades since I did reactive/imaginary electronics at university.
Please someone correct me:

80 ohm is fine from a phone or a laptop headphone jack. Basically everyday consumer not-special devices.
80ohm can covert the small power output to a higher magnetic field, so the voice coil can move more (or with more force) which moves more air, which is louder.

But to make 80 ohm coils, it requires a thicker wire in the voice coil (thicker wire lowers resistance. I know its impedance, but I feel like wire resistance is probably higher than the imaginary component). Which makes it heavier. Which makes it slower to change direction (heavier has higher intertia, so larger momentum once it's moving in one direction). So you get less definition (high frequency/fidelity/detail/whatever, basically).

P = I²R : as resistance increases for a given power amp, the current has to drop. And magnetic field (which drives the voice coils) is related to the current.
So for a given power amp, low impedance phones will generate more magnetic field.

So a low impedance headphone can do more with less, at the expense of fidelity/high-frequency/detail.

A higher impedance coil is made with thinner wire, so is lighter which reduces its intertia.
But it requires more power to produce the same amount of magnetic field (which relates to the amount of air moved, which relates to loudness).

I feel like the whole thing is a rule-of-thumb thing.

Generally low impedance has heavier components which move slower, so can't do the higher frequency things.
But they can move more air for a given power, just slower.

High impedance things are lighter and can move quickly. But they require more power to produce the same amount of magnetic field.
So they can move air faster for a give power, just less of it.

So a high power headphone amp will be able to "drive" 250 ohm headphones.

I have a FiiO k7 with my DT770 250 ohms.
It's a dac, nice big volume knob, usb, DAC (spdif copper and glass), unbalanced inputs and unbalanced outs.
My hatred (and I wish I knew this before buying) is that inserting headphones does not mute the analogue outputs. So plugging I. headphones doesn't mute my speakers.
Other than that, I have no issues with it. Sure, I'd love a Benchmark. But my budget says FiiO is good enough, and my 770s sound lovely

If you have a headphone amp that supports high impedance headphones, you can go with the 250 ohm version, otherwise use the 80 ohm version.

Both will get equally loud before distortion. But your amplifier need to support it.

Einzelne Firmen werden doch ständig von Konzern zu Konzern verkauft. Das heißt nicht, dass sich "am Boden" immer was ändert.

Mein aktueller Arbeitgeber ist auch eine deutsche GmbH im Besitz eines ausländischen Konzerns. Auf die Arbeiter und die Kunden hat das aber keine Auswirkungen.

Achtung!

For a while it'll be true. Then the strong German labor unions/laws will be seen as an impediment to profitability. Of course this won't be spoken aloud. However, the assembly jobs will be moved back to China piecemeal. (Not fast enough to alert lawmakers and cause a commotion.) Until finally the entire operation is in China. The name (which is the valuable thing) will live on - affixed to a fully Chinese designed and manufactured item. Sold on Amazon to people who don't know better.

Sometimes it happens before they are bought out like with Cherry moving their factory to China.