[kd3d]

Hello everybody, I'm from India. Here in my city, we haven't got much options for headphones in local/online stores. So I've decided to brought a decent headphone through one my friends in USA. My budget is around 125-175$.
 
Currectly I'm using a Sony MDR-XB300 which I bought a few years back for apprx 45$. Initially it used to sound like a blast for quite a few months, but afterwards, I started to feel that the sound clarity was not good enough, and the vocals were a bit muddy. So now I guess it's time to go for a higher-end headphone. I'm describing below what kind of headphones I'm looking for.

1. I'll be using the headphone primarily with my desktop and won't be getting any extra amp.
2. A minimal amount of noise isolation will be required(from ceiling-fan sound, cpu-fan sound etc.). So i guess any over-the-ear type of headphone will do, whether it's open-can or closed-can doesn't really matter, cuz' I'll be using it only inside my room. 
3. Cable length is not an important factor, but the cable quality needs to decent (though I'm not an expert in Headphones, I think the cable quality of my Sony MDR-XB300 is pretty decent).
4. Build-quality needs to be decent and this new headphone should last for atleast a couple of years without any mechanical wear-and-tear. As I'll be shipping it from USA to India, no hope for warranty
   
5. The "sound-quality"/price factor should be equal to or better than my current mdr-xb300..in other words it should be a value-for-money thing, not like overpriced headphones from Senheisser/Skullcandy (my personal opinion and I'm not an expert in headphones
   
   )
6. Musical choice :

Mostly I listen to death metals from different genres (melodic/folk/viking/power etc..) from bands like CoB,Insomium, Wintersun, In Flames, Dark Tranquilty, etc... more traditional bands like Disturbed, Metallica..etc. And some altern rock like Poets of the Fall. For the metals, my mdr-xb300 seems to manipulate the bass and the treble is neither good-sounding nor clear enough. And particularly in death metals, the vocals (read... the growls

) doens't sound much clear as they should be.        Pop/trance/hip-hop/funk/rap etc. are not my kind of music. Occassionally I listen to some Jazz/Classical/Altern.
I'll be using the headphone with my desktop all of the time, for listening to music, watching movies and gaming. But the sound reproduction quality in music is the most important factor for me and rest are secondary. 

1. Overall the headphone should be comfortable enough for long hours of usage. I've a small sized head and the mdr-xb300 does quite good in comfort factor. Earlier I was used a Senheiiser headphone borrowed from one of my friends (probably it was HD-208, but I can't remember it now) for a few days, and it didn't seem too comfortable at all.
2. Based on my noob experience, I've focused a few headphones listed below.

Audio Technica Lineups : ATH-M50, ATH-M50s, ATH-AD700, ATH-A700
Sony : Sony MDR-V6
Fischer-Audio : F011
As you can clearly see, my knowledge about of headphones is very limited, and I haven't even listed other popular brands like Grados, Kosch etc.
 
So finally I would like to ask you Head-fi expert users to help me choose the right pair of headphones in my budget. Any suggestions/advice are welcome in advance. And if you know the right place for placing an online order to get the best deal, please mention that also. And lastly, thanks a lot for going through this really long and boring post and helping me out