Somewhere posts that DAC can affect a lot, especially when you have decent headphones. Somewhere else says it only has to deal with mere noise floor and stuff that is nothing.
So what's the real deal? I have a Fiio X1 whose line out IMO feels good enough channeled through mid-high end headphones through amps. Or will getting the Modi 2 get me better quality?
Provided the response isn't skewed on one DAC vs another, and both are at inaudible levels of noise, chances are the difference is in the output level. Just a fraction of 1volt can make one DAC sound better than another if you don't adjust the volume control settings to match it. Similarly, most portable gear have considerably lower than 2volt output, so when comparing it to desktop DACs and you are aware of the difference in loudness, it
might end up with the amp at audible levels of distortion and noise.
Personally, barring some obvious design issues, the main considerations for a DAC should be connectivity options. If it can't work with your desired source or even the components downstream from it then it's useless. Second consideration is just aesthetics - do you like looking at it next to you amp, or would it stick out like a sore thumb, like if all your gear is black and then you get a DAC with a silver faceplate.