How did I miss this thread?! I asked questions about most of these headphones on the advacie thread, but no responses or redirecting me to this one. Glad I found it.
I don't know about m50x, but I've listened to m50, and I'm glad that finally someone expressed what I heard. Bass is really present, but it's so compressed. Sound overall was very compressed IMO, and I didn't like it at all. It was also not clear to me how people use them to mix, because of compressed sound they seem very hard to balance things on them, but I would have to hear them again tho. Also, drums were sounding more natural and punchy on KSC75 imo, even tho is a way cheaper headphone.
When it comes to NVX XPT100 it's a shame they have a hole in 300hz area, where the warmness is.