[Solude]

The amp and source are locked, Meier Concerto and Stello DA220 respectively.  So pick your number one contender to best the O2 as a one and only can.  Some limitations... no out of production models, no recables, and if you vote other, let me know which can I should also consider.
 
Huh poll went poof =(

 

[krmathis]

HifiMAN HE-6
Admittedly never heard it, but from reading impressions and reviews it does seem like a pair to seriously consider.

 

[Solude]

HE-6 isn't on the list because it takes a speaker amp and technically isn't in production yet.
 
NOTE: My second attempt at getting the poll to show is the active thread since it shows the choices the poll was supposed to have.