[Phishin Phool]

I was considering one of these three as my next set of cans could somebody please give me as best a description as you can of the differences/similarities between the three and relative comfort of each - many thanks JK
 
I would be looking for a more neutral sound as my current 'fun headphones' which I like a lot are DT 990 pro 250Ohm
 
I have both a Project Sunrise II amp and a Fiio E17 DAC/AMP (although I may be upgrading the Fiio DAC/AMP shortly)

 

[KG Jag]

The HD 600 is the most neutral of that group.  Both it and the HD 650 are well described in this excellent piece:
 
http://www.head-fi.org/t/634201/battle-of-the-flagships-58-headphones-compared-update-audeze-lcd-2-revision-2-6-4-13

 

[kookoo]

For something more neutral then also consider the Audio Technica AD1000X and the Sony MA900.
the battle of the flagship article as stated is a very good starting point do check it out