It’s all important, but from what I’ve heard from other hi-fi enthusiasts much more knowledgeable than I (and judging with my own ears, which may not be as keen as others’) it is the quality of the power supply and the type and quality of the output stage that make the most noticeable difference in a DAC’s sonic character, given that the clocking and conversion are above a certain standard of performance. Again, I’m sure others will disagree, but that’s been my experience.