To clear a few things up:
1. The new USB Gen 2 input is really, really good. I'll put it up against any converter under $500, and many over that price. Why? Because even with the best USB-SPDIF converter, you're still dependent on how good the DAC is at SPDIF. Now, Gungnir is VERY, VERY good at SPDIF due to the unique Adapticlock system--it is the only DAC out there that assesses the input center frequency and jitter in order to assign it to the best clock regeneration system. But the USB Gen 2 measures even better. Now, measurements are not everything, but the fact remains: USB can outperform SPDIF, at least in measured performance.
2. The Gungnir's USB input doesn't need any conditioning, auxiliary power, cables that cost more than Gungnir itself, plutonium rectifiers, magic faerie dust, rituals involving swinging a dead chicken by the light of the full moon, or any other quantum arcana in order to achieve top performance. Get a good USB 2.0 cable. Connect it. Done.
Hope this brightens everyone's day!
All the best,