> but the thing that disturbs me with them is that every model in
> their range sounds totally different in terms of sound
> character.
I think that's the nature of headphones, and all speaker technology in
general. It's often like trying to decide which food you like best...
picking one "flavour" of sound over another depends upon your mood, the
circumstances, and -- of course -- your budget. There's no such thing as
best, but there is definitely such as thing as too cheap :-)
The 580 set are very impressive, though I also like the Beyer DT range for
quality & comfort (obvious given they're widespread professional use). My
Bose noise cancelling set also sound excellent (definitely a different
"flavour" to the Sennheisers though), but due to their compact & isolating
nature, are less comfortable to wear than the weighty, but low
pressure 580s.
The Sennheiser radio headphones (HDR 65 circumaural in my case) are
noticeably poorer quality, but you're paying for the freedom rather than
pure quality. And that freedom is great... except when you forget which
set you're wearing and start breaking leads, which can get expensive very
quickly with decent headphones!
As with so many things in life, chasing the "perfect" all round headphone
can get expensive, and it's easy to end up with a collection that suit
different circumstances but rarely get used because it's frequently easier
to just reach for whatever's closest!
Still, everyone should have a hobby ;-)
Andrew McP