Hmm, this is probably a weird ask, but since the A8 can be a DAC, pre-amp, and player, I wonder if it is possible to play to an external DAC, but then have the external DAC output back into the analog inputs on the A8, and the A8 to then act as the pre-amp at the same time? The reason is that then any amp downstream can be connected just to the A8's analog outputs, and the user can get a choice of two DACs. Use the A8's internal DAC sometimes, but also have an R2R DAC or a super-analytical ESS DAC as an alternative option.
Also, the product page shows that there's a DSP suite in the A8. Parametric EQ, loudness correction, compressor (but no expander?), and delay. That doesn't seem to be present on the A6, and it appears to affect most inputs. Very interesting...