Best USB DAC with Grado Head phones

I am searching for a USB DAC for my computer / head phone rig. I don't care much about a DAC/AMP combo since I plan to buy a separate headphone amp. Using Grado's GS-1000, RS-2

I have narrowed down my search to three DACs:

Benchmark DAC 1 USB $1275

Bel Canto e.one DAC3 $2495

Wavelength Cosecant USB DAC v3 $3500

The concern I have is that in both Stereophile reviews of the first two DACs, the USB performance was inferior to the input using S/PDIF and AES/EBU sources. There was no good explaination for this in the articles but may have been in part related to setting the iTunes preferences correctly. The Bel Canto seemed to have higher marks than the Benchmark DAC 1 USB but not by a differential of $1200. Furthermore, the 24/96 capable USB option is still not out yet.

Has anyone heard all three yet to compare????