I have pretty much decided to buy a pair of Beyerdynamic DT990 pro headphones. The question is, which version? Most people seem to favour the 250ohm model. Is there any difference in sound quality between the 250ohm and 80ohm models? I don't have a headphone amp at present but would be willing...

I normally use a pair of Sennheiser HD600 headphones and I enjoy the sound they produce. I listen to mainly classical music but not exclusively. As I am something of an amateur sound recordist I also own a pair of closed back Beyerdynamic DT250's which I find useful.   Now to my problem. The...