Sounds like you’re in a similar place to me
I was finding the M50 to give me slight headache quite quickly with certain music and unsure if it was the bass or treble doing it. I use it on laptop ,iMac or iPhone ( though also use dragonfly cobalt with iPhone which makes an HUGE difference).
Here’s what I tried: Sennheier 660, 70x, Sundara ,Aria stealth, and a couple of others.
The 70x was no where near as good as the Sundara, and the Sundara was better than the 660. The soundstage of almost anything is better than the M50 but none of those had decent bass never mind as near as good as M50
The Aria: sure out of budget but got to be tried. The soundstage is crazy good. The bass better than the others but still way short of the M50.
Apart from the soundstage, the Aria wasn’t THAT much better than the Sundara except perhaps for the bass, where the Aria made up for the almost complete lack of it on the Sundara ( Sundara was still better than the 70x, 660 though)
The M50 can be a bit viscious but boy does it have good bass making the Aria sound very digital esp. with drums etc, tinny almost ( but that’s most likely due to not putting a proper HiFi Amp with it) But the clarity of the Aria and soundstage is phenomenal
I came away from my trials deciding to put up with the foibles of the M50 a bit longer until I could afford the Aria and a proper Amp. to pair it with. And new cables as the ones it comes with are noisy as hell if the scrape on anything.
I realised during the testing which took me ages, that although the M50 has some annoying traits, it is hard to beat in other areas. In fact it was s relief to get back to the M50 lack of soundstage from the Arias which are almost too much as I found my eyes following the sounds about all over the place. That huge soundstage is initially incredible but gets wearing after a bit.
Had I not got fed up with testing my next thing would have been to see if there’s a closed back Sundara ( I think there is) with as good a sound as the open back but with better bass.
The Sundara came out highest in my overall estimation especially for value for money. It’s noticeably better than the 70x, 660, and M50 in every aspect except neither it nor or the 70x of 660 have any bass to talk about. I really don’t like excess of overly dominant bass but I do like it to be clear and present.
I did try classical, techno, trance and electronica in my tests but mostly I listen to jazz/reggae fusion, dub, jazz, ska etc
If I HAD TO chance my headphones now I’d get the Sundara. As I can wait, I have realised that it’s probably more important to get a high quality amp first, before doing more headphone testing as that’s a limiting factor on the performance of the more expensive headphones