Audio science review is the antithesis of this forum. There people think the only thing that matters is the numbers--if it has the lowest THD and noise floor, it must sound best. Here people think all that matters is what they hear, even if their claims violate the laws of physics.
The answer is somewhere in between.
I think the DAC is very important to the sound in a modern digital system...I’ve sometimes said it is the most important component, but that is easy to say when you have the amp all dialed in...I will say that the DAC is the most expensive component in my system.
His claim about a $400 DAC shows that he isn't listening at a very high level.
Jerry