[DjAmTraX]

Has anyone compared the two units?  Which is a better headphones amp?

 

[funkmeister]

Way late on this one, but the DAC1 has better gain stage selectibility and a higher damping factor. Most people can't tell them apart, but occasionally there are nags about uneven frequency response from the Grace. I haven't gotten to the bottom of that. Also, the Benchmark runs native current from the DAC stage through the differential op-amps... all in current mode for the fastest transient response with the least distortion. Their THD+N is insanely low and it runs cooler than the Grace.

 

[Wapiti]

I have a M902 and a DAC1. 
 
I prefer the DAC in the Grace and the DAC1 as headphone amp, but they are both very good at each.
 
I do most of my recreational listening via a Woo WA5.