Harmon,
The SACD signal is not passed through any digital output. From what I can recall SACD is licenced for the player only, hence no out board dac is available. CD and DVD-A digital signals can be passed through the output to an external DAC, but the DAC must be able to handle the different bit rates.
Look into the Altmann Attraction DAC, there is a optional bit rate switching feature, that can be used to switch from rate to rate depending on the recording format. Also look into Lavry products, I think they will automatically switch depending on the signal provided.
Hope this helps,
Rodge