I ended up ordering the Momentum instead of the M50x because they're within my price range (it was 18% off), they have a more organic sound, not as punchy bass as M50x but it has a warmer bass (warmth in music is really important to me, more important than punch, if I could I would go for both/something in between), the highs are not fatiguing on higher volumes (I can easily get fatigued from using certain headphones), they have a nice focus on mids and they apparently sound "heavier" (if I interpret that correctly it's going to fit my type of sound signature), also my old Sennheiser PC360 headphones have a sound signature that fits me almost perfectly (except that they're open-air so the bass is lacking), the PC360 however is slightly lacking on everything and gets distorted easily on higher volumes, but the balance of everything fits me really well, so despite the fact that my D600 produces more of everything and overall has a better sound quality, the PC360 is actually kinda my favorite because the balance of everything fits me really really well (except the lack of bass of course), but I haven't used them for several years since the D600 manages to play louder without distorting, they produce more than twice the amount of bass and has more of everything.
When I said the D600 is a bit lacking in bass I probably exaggerated, the D600 doesn't lack bass at all actually (compared to a speaker setup they definitively do, but compared to other headphones they don't), but it lacks certain parts of the bass to give me exactly what I want, but it would be almost impossible to find exactly what I'm looking for unless I was willing to put in some serious cash. From what I've read the Momentum definitively has less bass than the D600 and might have a bass signature that is further away from the D600 and what I'm looking, but since they're not going to be used at home it's not a problem, and from what I've read I'll easily enjoy the Momentum's bass signature because of it's control and warmth, I'm also sure that the music I have on my phone is going to go nicely with the Momentum.