Horses for courses, so many independent variables, and the onward march of technology.
If the built in DAC (operating in the electrically noisy EMI/EMF environment ) in a system with moving parts is what you want in your listening environment, then the one box solution may be exactly what you want.
Other people have commented on the fact, its not just the dac, but the power supply and the analog output stage that are determining factors in audio quality.
Add to that the mastering of the source material, over and above the container features (bit depth, sampling rate) .
It strikes me that the inbuilt DAC is a sunk cost if you want to upgrade later to something "better" , or e.g. you have an external parasound DAC you prefer.
Competition is good. Choice is good. What can you change, what can't you change? what's likely to change in the future ..
In the absence of "Magic" these are deterministic systems. What's the lowest cost way to achieve the desired result?
Note: Desired result may vary by persion wrt. user experience / complexity / appearance / cost.
This may indeed be the "Best" system for you. Based on your requirements. Assuming they don't change over time