There is quite a bit of information available in the various reviews of players that suggests the quality of the player is important to the quality of the sound produced by the DAC. You can't expect a PC or Mac, or any computer with a hard drive to be as quiet, or sound as good, as a player, which is designed to minimize noise and interference in the signal transmitted to the DAC.
But... I've found that the DAC makes a huge, huge difference in the sound quality of the combination. I have a number of both, and I've found the sound quality of the Bryston BDP-3 is about as good as it gets for the money (very quiest, very clean signal), and anything above that is likely diminshing returns.
However, I've found the Schitt Yggdrasil is far and away about the best DAC available - just a whole lot more real / live sound, with all of the resolution, transparency, clarity and vibrancy and holographic sound that you will find at virtually any price. But, as you would expect, the rest of the system must be able to present the sound that it produces, including the player.