Im shopping for a new pair of headphones,currently i own a pair of 668b which i love,but i would like to upgrade and use my 668b primarily on my Guitar Amp for practice sessions. i know that the M50x and 558s are completely different kinds of headphones since one is Closed-Back and the other is Open-Back. now i do have a problem with Open-Back since i share the same room with my college roommate,he uses a Closed-Pair so im fine for most of the time but when he is studying or sleeping (usually i stay up late) he can hear what i’m listening to,so im leaning towards the M50x,but i would like to know which one of these two headphones would be best for Hard Rock/Classical Rock/Progressive Rock/Metal/Death Metal/Black Metal/Power Metal and some electronic music. And i also plan to use them for Gaming and Movies,im not a super competitive FPS player (or else i would have settled with the AD700x) and im no Basshead,but i do enjoy a tight bass for gunfire and explosions. if you own or have used both these pairs i would like your opinion.