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Got my SGS2 yesterday and so far have been very impressed except with the music playback. I upgraded from the iphone 3gs and the music playback through my headphones is nowhere near as loud. This kind of sucks for me as I regularly use my phone at high volume levels (ears ringing after) to pump me up while I walk to the gym and also being a heavy metal fan, non moshing volume music just won't do. 
 
Now I'm a total novice/noob to headphones so hoping some of you could help me out here with what to do. Is it naive to assume that a better quality headphone will increase the max volume it'll play at? I'm currently using the Sennheiser CX500 which was a huge leap in volume from the rubbish headphones that originally came with my iphone. Can any of you name any headphones that are slightly higher in price but offer louder volumes?  I live in the UK so it'd have to be available here.. I've had a little look and prepared to stretch (and sadly it is a real stretch) my budget to get the Sennheiser IE7 as I found it at a great price (half the retail price). I also like the look of the Sony MDR EX500LP. Would any of those offer a better listening experience with volume boost being the primary goal?
 
Thank you all for your time and any advice on my situation would be greatly appreciated.