Two SPDIF inputs (RCA & BNC), toslink, and USB would cover most users. Because DAC technology is evolving, it would be great to see that section in the form of an upgradable module that could be end user replaced as upgrades are release. Just slide it out like you would a channel on a 2B-LP.
...if this is doable with this new preamp why shouldn't it be possible to have an upgradable dac module for the BP17³ and the 135? that way the customer can choose what kind of digital input he prefers for his setup. i might be wrong but i think that a more compact solution is a nice option for those who doesn't want another box for another box, etc. the BDA-3 surely is a cool performer but maybe some people don't need 10 digital inputs. what i'm trying to say is that if Bryston would offer digital cards with different inputs for the 17³ and 135³ it would make them more versatile for different needs.