Marketing likes to stick all kind of lines into adds but you know how marketing should be treated...
Sure good modern sound cards drive about all headphones to sound pressures making hearing head toward "early retirement" in minutes.
But for fully driving some 600 ohm headphones in all situations (peaks of high dynamic range music) wouldn't exactly trust any sound card to have enough reserves for that.
Anyway there aren't even much of 600 ohm headphones available.
Though impedance is far from everything.
What isn't so commonly advertised is that different headphones have different efficiency in making sound from electric power.
Some Hifimans can need almost thousand times as much power for same sound pressure than highest efficiency IEMs.
AKGs are also below average efficiency cans so despite of lowish impedance they still need some amount of power.
Similar impedance HD598/9 Sennheisers would output lot more sound at same volume setting.
Common 250 ohm Beyers with their average efficiency are rather easy load with neither highest voltage or high current need and are insensitive to output impedance.
(TPA6120 of that Asus card is specified to need 10 ohm output resistor to stay stable)
All versions of Beyers have same efficiency and hence same power requirement:
32 ohms ones just take power as higher current from low voltage while 600 ohms ones need lots of volts but very little current.
For gaming use Beyerdynamics have one nice bonus:
If you ever need to have microphone it's easy to attach normal microphone to them if ModMic's price tag looks expensive.
DT770 mic mod
Any way first thing to narrow down is do you have quiet environment or need isolation of external sounds?
Besides no additional sweating from open headphones their overal sound and sound stage is often lot better for positional audio/binaural sound.
Closed headphones, even better ones, tend to have always quite lot smaller sound stage...
And cheap Chinese gaming junks are like putting head into bucket.
Also if you want maximum competitiveness meaning easiest hearing of foot steps etc bass neutral headphones have starting advantage in that.
Though "shy" bass eats fun factor badly so it's always compromise.
And equalizer can be used to tone down bass if needed.
(and without any danger of sound quality degradation unlike in boosting weak bass)
So likely you want headphones with good robustness in bass, but without it drowning everything else, like in cheap junks.
Beyer's DT990 balances nicely in that. (coming from bass neutral HD595)
Most AKGs, like one of the best for competitive gaming K701/702 are quite bass neutral.
K712 heads toward DT990's balancing.
Sennheiser HD598/9 are again good for that competitive sound with "no fun" neutral bass.
More bass robust HD600/650 seem to be aimed for enjoying from music with more compact sound stage...
Instead of "those shots sound truly like coming from dozens/hundred meters away" sound.
This is very good for testing headphones. (everything sounds coming from next to ear with cheap closed design junks)
Earlier Asus cards used that gothic cathedral/public bath called Dolby Headphone but I have no idea what those latest Strix cards use.
Might be just more common downmixing to avoid paying too much licensing fees.
I think maker of codec chips used in Asus cards has its own one, which would be likely cheap enough.
Sennheiser GSXes are essentially how gaming products are made:
You take cheap ass Conexant DAC/output buffer chip meant for phones/tablets and below level of £30 sound cards parts and sell it with huge profit margin.
Even integrated average Realteks are better.
As car comparison that Asus would be Jaguar/Rolls Royce and GSX Morris Mini.
Astro's Mixamp is likely at similar level and most headset USB dongles likely even cheaper.
And it and lot others use that apparently cheaply licensed Dolby Headphone.
