Why would you need that? Coolness factor? ;-)
If you're not going to record or connect your Mac to some outboard gear via digital cable (external DAC, DAT recorder etc.) but all you need is analog output, I can tell you that output circuitry of SAII NuBus and SE/30 cards is identical to that in the A/D box pictured above.
* Same convertors - Analog Devices AD1856 or pin compatible Burr Brown PCM56.
* Same encapsulated Murata low pass filters.
* Same I/V stage ICs - NE5532
* Same red WIMA 1uF capacitors
.......everything..........
All you need is Y-split cable to go from jack to RCA (Cinch).
EDIT - oh, ok, Digi used "audiophile quality" WIMA FKP caps (green boxen) in filters instead of blue NP0 ceramic ones on cards, but that's the only difference.