Headphones with different impedances

[dave2010]

I just noticed this https://www.amazon.co.uk/beyerdynamic-770-PRO-Studio-Headphones/dp/B008POFOHM/ref=sr_1_51?ie=UTF8&qid=1516255903&sr=8-51&keywords=headphones

This appears to be an offer for essentially the same headphone set, but in a choice of different impedances.

I've never seen headphones of the same type offered with different impedances before - though maybe I've not been looking.

Is there a best impedance to use? Also, if buying with other kit - such as a headphone amplifier - is there an impedance which is a best match?
Presumably if one already has kit one matches to that, but if there's a completely blank slate, what then?

[Lawrence001]

When using an OTL headphone amp (eg little dot 3/4) it's generally best to go for the highest impedance as this minimises the power loss across the "internal impedance" and valves are better at voltage than current in the P=VI equation. Sorry if that's not strictly technically correct but it's how I think about it.

Conversely solid state can struggle with very high impedance headphones and you're better off with the 50-100 ohms range depending on the output impedance of the amp. Please correct me if I'm wrong her.

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