Maybe have a CD transport source USB to drive a USB DAC?

[wa2ise]

It looks like USB DACs have the frequency reference of the entire music reproduction chain at the DAC, and the source (be it a computer or such) transport device is slaved to that frequency reference. Thus no jitter issues that you get with SPDIF. The USB DAC would ask, from time to time, for packets of digital bits to keep the DAC outputting music continiously. There would be FIFO buffers in the transport box and inside the USB DAC chip and handshaking over the USB cable.

I don't know all the ins and outs of USB, but if a USB source in a stand alone CD transport box is able to talk to all possible USB DAC chips on the market without having to make the user go thru the agony of configuring the transport box, then USB could replace SPDIF.