>>107022325
>hd599
I'd get 6XX over those. Not because of better performance(in fact, 599 might distort less) but because it's far more comfortable than anything in in the 5x line. It's also easier to repair since you can take it apart easily and there are replacement parts everywhere.
>dt990 pro
If you don't like treble rape I wouldn't recommend them. Get 6XX or if you want something with less bass distortion there's HE400SE but it has the shittiest QC in all of audio so probably not worth the risk. Chinkfiman is chinkfiman for a reason, after all.
>>107022450
I've had my 2Cs since launch and they're still fine. I've heard Audeze's QC has gotten worse since they were acquired by Sony, though.
>>107023786
If it's not the 250 ohm version then a US apple dongle would be enough to drive them. If it is the 250 ohm version, yeah, sure. I feel like Schiit's products have become shittier(haha get it) in recent years but ignoring whatever potentiometer issues some of their stuff has, performance is very good. So yeah, a Schiit stack would be fine.