Well I trialled the HD650 versus the HD595s. Got to say that I have definitely reached the land of general impression and the last 10% of gain rather than a real step up.
Sound was more forward in the 595s, more transparent almost translucent in the HD650s. More of an atmosphere thing that is hard to pick up on unless you just close your eyes and feel rather than actually listen.
Got to also say we're into teh last 10% of clarity and detail - I can't deny there was an improvement.....but you have to really force yourself to hear it.
The key about theHD650s for me however was that you just sit back, relax (they are the most comfortable cans I've tried) it's like you are wafting along in a bentley or rolls royce whereas the HD595s felt more like a mercedes AMG. Less refined, less mellow, more forward, definitely way more veiled. Bit like a raucous child in comparison to something more relaxed. Perhaps it was placebo - perhaps I was looking for what others said but what I was stunned at was not my ability to really easily pick out instances where HD650 was better - but just in the whole experience/package. Bass is pretty much the only place where the hD650s really outpace the 595s. In fact with my current cans quality bass is the area where I am really very lacking.
Have to admit the amplifier I was using (First time with a tube amp I think!!!) made them both sound beautiful.
The guy in the shop asked what setup I had and I said I was going to get a MD-10 as a Dac and he tried to push the Benchmark DAC1....Hmmm....perhaps that will 'synergise' with HD650
As for the cables - guess I'll get equinoxes if I get the HD650 since everyone raves about them.
Home Amp+dac is for another day though.
source - marantz CDP --> X-canV3 amp btw.
In summary - got to say I'm really torn about buying the HD650s - yes they are lovely and amazing, but really you have to put yourself into the right state of mind and start microlistening to really hear the benefits. I guess I can trial them for longer out of the store and see if their 'environment' warrants the £160 for the upgrade.
HD680 might be coming soon though :S
Not as if I really need one either.