I just got my account here and i need your suggestions. I have sennheiser hd 25 sp ii and i want to upgrade my headphone. Music types : Trance, house, minimal ... I am looking for good isolation and comfort with long time usage. I couldn't decide between ultrasone pro 900 and beyerdynamic dt 770 pro. Mostly i will use it with pc. I can buy an amplifier if it worths for beyerdynamic dt 770 pro. Therefore i need your ideas. I hope you can help me. Another thing is that, ultrasone pro 900 is almost twice (in price) in my country. I would like to know whether it worths to buy or not.