Fiio K5 Pro x Audio Technica ATH-R70x


This is my first post here, so please forgive any mistakes I am still getting a foothold.
I’ve recently started a new job and wanted to get some nice audio equipment to use during and after work.
I’ve got my eyes on the Fiio K5 Pro and the Audio-Technica ATH-R70x Open Backs, I can get them for around £250 and the Fiio for around £150

Looking through the specs of both, it seems that the Fiio is only rated up to 300 Ohms headphones, whilst the ATH-R70x is rated at around 475 Ohms.

I understand that the Ohms is a measure of electrical resistance within a circuit / component but I understand very little past that.

My major questions are will the Fiio K5 Pro drive the ATH-R70x properly? Will it sound good? And should I really worry about resistance when purchasing headphones or is it only a worry when you get to around 600 ohms?

I’m looking into all of these but a lot of the info is confusing.

Neither do many people in this hobby.

In case of interaction between amplifier and headphone, resistance is how hard (= voltage) the amplifier has to work to get current flowing.

Given the specs Fiio provides, some napkin math:
217mA maximum current (their 1.65W into 16 Ohm does not quite add up here)
20V peak-to-peak voltage swing (limiting factor into the R70x’s)

Power = Voltage x Current = Voltage x (Voltage / Resistance)
10 x (10 / 470) ≈ 0.2W

Why half of p-p Voltage?

Because going backwards in your car to measure acceleration, you are also testing the breaks.