Best Digital Interface

It is my understanding that Asynchronous USB may be the best interface for digital transfer to a USB DAC. If the DAC has  Asynchronous USB then it basically owns the signal and basically re clocks timing, bits etc for a more perfect transfer if fed USB? I am streaming from a Node 2 into an RME DAC. I know there is no USB output from the Node. I have a few questions: 
1. Is there a Coax to USB adapter available? Does this make sense? 
2. Are there other reasonably priced (>1k) streamers that have USB output?

Thanks!