I think I can answer your concern. If you like HE-560 and 400i, you will definitely like HEX. HEX will give your much more resolution. I do not find any treble problem. I used to own Beyer T90, which is definitely too bright. I want to describe HEX as better HD600 with much more bass. (As for the bass, you actually can feel the vibration when you hold the HP and play bassy songs.) So do not think HEX as another HD800. You don't need any EQ for any genre of music, IMO.
I actually have similar comparison (Elear) when I bought HEX. People think Elear is kind of too intimate, which is like higher resolution HD650. However, it is still dynamic HP. Planar magnetic HP is very different. HEX will have larger soundstage and give you the HEK signature. Also, people will find they spend more time with HEX than Elear and HD800. People actually want to compare this HP with Ether Flow.
Btw, good DAC and amp combo will really bring out better experience with HEX. You are not looking for more power but your preferred tonality.
I hope these comments can help you.
I may have been unclear, I already have the HEX.
It is odd, certainly. As I said, I also recognize the treble not being the most clear/forward, and it's not supposed to be the case with these headphones, but boy can they hurt my ears, at least as much as an un-modded HD800. When I say hurt, I mean something making my ears physically painful inside. I had ended up selling my HE-560 for the same issue, although on a smaller scale.
It did get a bit better out of my Creative X7 though (Bottlehead Crack is awful with it, but that's to be expected.)
Damn sensitive ears, right?
As efficient as they are, I do find they respond very heavily to the amp/DAC used.
I'm going to give the Chord Mojo a try since it's not only known as a good DAC I've wanted to ear, not harsh either from what I've read, but also a great pairing with the HEX, and report here.
I'll end up giving the Elear a try out of curiosity anyway (cause intimate+higher resolution HD650 is actually really appealing to me, as well as its other characteristics) and it's also a good combo, apparently.
The HEX doesn't really have the magic the HE-560 & HE-400i had on me for now, but you never know.
The 400i was probably my favorite. Definitely nothing impressive about its soundstage, and you might wonder why the HEX in this case, but I wanted to try it considering how much I liked the two other HiFiman's.
The HEX signature's pleasant, that's the better word to describe it, just not emotionally involving to me for now. On the contrary, they have a bit of the HD800 symptom where I'd get tired of them past 30 minutes or so.
If I had to give my biggest gripe about them, it would be the lack of body. I was just hearing a few piano notes as the end of this writing and was thinking "Damn it, slam these notes!".
Well, thanks for taking the time to answer anyway! You know, at the end, ear pain might actually settle this without too much thinking if it can't go away