That depends on whether you want to match the source (mcx8000) impedance with the headphones (load) impedance.
If you use headphone without built in power amplifier it is best to match de source impedance with the headphones impedance and I advice to choose wisely if you also want sound fidelity.
Usually high fidelity headphones use a higher impedance, but many audio equipment manufacturers use an output source impedance of lower value in order to be used with a greater range of headphones, from cheaper to more expensive, but the trade off is power loss.
Ideally you should match the source impedance with headphones (load) impedance and to take into consideration the headphones sensitivity in order to obtain a good sound quality.
Some good quality headphones have built in power amplifiers in order to compensate the difference between source and load impedance.
If you decide to use unamplified headphones it is best to match their impedance with the impedance of your audio equipment headphones output. Also be very careful when choosing headphones sensitivity, because very sensitive audio headphones drivers require less power to reach a certain volume but lose fidelity and lower sensitivity headphones drivers may provide sound fidelity but lose volume level. It’s a balancing act.
No matter if you use higher or lower headphones (load) impedance you will still have a loss of power (load loss). Even if you match exactly the source impedance with headphones (load) impedance you will still have a load loss of a few dB.
Regarding headphones sensitivity I can recommend you to choose something between 100-110 dB / mW and with an impedance between 40-50 ohms.
Also, if you want to use your headphones in a noisy environment I advise you to choose headphones with high power range to be able to connect with high power source equipment.
At last, the frequency range of your headphones are very important because you want to hear the sound details, but this is a matter of personal preference.