One thing you messed up....the HD 600's are $350, the 400i's are $490. How is that double the price? 

This based off Amazon brand new. 

None the less, good review! 

As above, the HD600 is frequently on sale. The 400i, not so much, though do talk to Brian Larson at RazorDogAudio if you're interested in that one.

Agreed, HD 600 is sweet and non-fatiguing, for what I've learned, natural sound is the base sound perception of our brain, so sometimes at first more colorful headphones seem quite interesting, but for long usage, you'll get back to natural sound, as for me AKG K702 fit my preference best, HD 600 come second, and T1 the third.
 
Cheers ^^

alexdi, thanks for this write-up.  If Head-Fi could somehow make your whole section on Source Material / DAC-Amps / DSP a blanket intro to every headphone review, it would save so much wasted discussion on these topics.

That's kind. I'm a bit constrained by the format, but this model is popular enough that it might get a few eyes. 

Brilliant review! But where is it on sale (brand new) in the low $200s?