Not meant to bad mouth the HP50. I actually love mine to death, its just that I want another headphone that has better soundstage and great vocals. No doubt the HP50 deliver on those fronts, but I do hear other cans that do better (eg. MDR-1R works great with female vocals, Open headphones has more airy soundstage) and it so happens that I found the K550, which is touted to be an open-sounding closed headphone. It will not replace my HP50, but would it have better soundstage and mids? If not, I will get IEM instead, and save my HP50 from all my sweat in this hot weather.
If you're interested in an iem with good vocals and soundstage you might want to check out final audios heaven range as they do that very well.