[chenwei95]

they are all used, 558 and momentum are 2 weeks old, m50 is 1 month, which one should i get?
i really like how momentum looks, but i use computer for hours and i heard it gets uncomfortable for long time usage
also, have the creative titanium hd sound card.
thanks!

 

[Zojokkeli]

If you are looking headphones purely for home use, I recommend the HD 558's. I own HD 598's, and I suppose the 558's will sound more or less similar (amazing) and they are probably as comfortable (I could easily wear the 598's all day if necessary, they are that comfy!) They are open backed though, so you can't really use them outside or in noisy environments.
 
I have also owned the Momentum on-ears. They are very good looking and not too shabby either sound quality wise, but they aren't nearly as comfortable as the HD 5X8's. I could wear them for a couple of hours, but after that they start to get a bit painful. If you want headphones on-the-go, I recommend the Momentum on-ears.
 
If you want my opinion, get them both! 

Otherwise, buy the HD 558's first and later you can get the Momentum's to rock on out and about.