Many audiophiles fall for the snake oil and myths surrounding modern digital audio systems.
The holy grail of "straight wire with gain" has been achieved (and surpassed) - in digital audio.
Unfortunately the input and output stages (the microphones used for the recording, and the speakers, cabling and amplifier in your room) are analogue, and therein lies the problem. Even your brain and your day to day physiology plays a part in what you finally hear.
Digital audio is simply 1s and 0s. A 0 is represented by no voltage and a 1 is represented by voltage. But digital is smarter than simply that. Since voltages in a system are analogue, digital works on a range of numbers. If the 1 needs to be 10 volts, digital can treat any value between 6 and 12 as the 1, and any voltage between 0 and 5 as the 0. Read that again. This is absolutely critical in understanding why digital simply does not care about the issues that plague analogue systems.
Here are some numbers to give you a better idea:
volt 02 09 02 01 08 11 01 12 02 03
digital 0 1 0 0 1 1 0 1 0 0
It is because digital is so forgiving of the analogue world it lives it, that it is precise and absolute. Imagine a legal document being emailed to you with errors. In the very rare instances it can be corrupted, but when it is it'll be very obviously corrupted. One does not pour through every word to ensure there are no spelling mistakes.
So, ask yourself. How can digital audio files be any different?
They are not.
It does not matter one iota if it was raining, the voltage in your home power supply was 110/220 or 111/222 volts that day. It does not matter if the power supply cable was oxygen reduced solid gold or a 5c cable from a junk store. Digital is designed to ignore such analogue induced errors - you get 100% output from what went in.
The DAC (or ADC) one uses has two sections within it, of course. The digital and analogue. Differences in the digital portion are minuscule - if that. Here's a thread that is trying to find out if there are differences. But all a DAC does is take the 0s and 1s and put them out as sine waves. These are just mathematical numbers undoing what the original ADC capture process did. Can one take the approach that these digital differences are zero (or so little as to be impossible to hear unless one has a multi million dollar system)? Note the emphasis on digital.
Once that DAC has created those analogue sound waves however, anything goes! The DAC chip in your laptop is essentially no different to the DAC chip in your external USB DAC. Any differences now lie in the analogue stage.
By all means spend your money on (analogue) loudspeakers (the most important component in your audio system) - or headphones, or on (analogue) room treatments (the second most important component in your audio system. Changes here make a big difference in how your ear/brain/body hear such playback.
In the digital realm it is - essentially - a straight wire with gain.