Mahgister- "you don't know what you don't know". In this case, this doesn’t have anything to do with system synergy, IMO it has everything to do with the quality of the dac and the preamp.
A lot of dacs are noisy when using as a preamp so a preamp is a requirement. Some dacs like mine have attenuation to compensate if there is any noise going directly to the amp.
Before ps audio came out with their BHK preamp, Paul’s recommendation was to go directly to the amp from their dac. I had a new $5000 preamp a few years ago that I used with my dac, and other sources. I took the preamp out and went directly to the amp, played with attenuation, and the sound quality was the same, so I sold the preamp. The BHK preamp might be better than the preamp I had, but when looking into making the dac sound best, most of the conversations I saw was to get the dac to perform best in its sweet zone, and this involved using or not using the attenuation feature. For example, some people claimed the sound with attenuation on sounded more smooth, while others claimed it was lifeless. Same goes for attenuation off.
Let your ears determine what sounds best after you run thru the many different configurations.