Yes it has, and I have looked at several such converters; not this particular set, though, so I will most definitely study this more later, and thanks for posting this.
I guess I kind of instinctively have been looking for a way to avoid another digital conversion, on the theory that more conversions could mean more chances for errors to be introduced, although I have no particular basis for that theory. Still, I like my old DAC and I like the AIFF files I have stored from CD and if I really want to hear the two together this may indeed be the best way to go about it.
In researching this, I have most definitely come to the conclusion that if I were designing a DAC, a USB input would definitely figure prominently into the design goals. Pity that the digital world can never seem to settle on one all-purpose I-O/transmission format.
Thanks again!