There is this audiophile article [0] that takes compares some different consumer level NAS devices. They used the same listening setup to play lossless audio files from different NAS devices. The article's authors perceived a difference in sound quality and characteristics, depending on the NAS and RAID configuration!
The article is a solid example of a placebo effect. The bitstream is identical between the setups.
When it comes down to digital to analog conversion, there's a lot of variables going on. I can definitely hear the difference between my laptop's headphone output and the headphone output of my prosumer-level audio interface. A more expensive audio interface might introduce measurably less cross-talk and noise. Some headphones will sound weak if the headphone amp is not powerful enough.
In other words: some people focus on things that are measurable. Others seem to be deliberately chasing the placebo effect of expensive equipment.
0. http://www.enjoythemusic.com/hificritic/vol5_no3/listening_t...