From what I can tell the Auralic Vega has a very good USB input (i.e. supports any format, hi-rez or not). So there probably isn't much of a need to use an external USB - SPDIF convertor between a computer & this DAC : in fact, the results may be worse. In my case I only use one because my mac mini is my server, the toslink optical is inferior to the USB, and my DAC (a Bel Canto 1.5) doesn't have the most advanced USB input (it's not asynchronous & doesn't support the highest resolution formats).
I think USB / SPDIF convertors are a stop gap product that will start to disappear as most new DAC's have USB 2.0 asynchronous inputs that support all the way up to 24 / 192 (and in some cases higher - like the Auralic Vega).