dCS does not use off the shelf DAC chips. They do all their filtering in FPGA, which allows them to evolve the algorithms over time. The Rossini will get firmware 2.0 shortly.
From the FPGA the signal goes to the actual digital analog converter, which is a dCS bespoke design called the
Ring DAC.
Whether the dCS DACs measure better than a Topping D50, I cannot say.
All I can tell you is that the dCS DACs sound very different (and to my ears more musical and less fatiguing) than anything else I have heard. This includes Berkeley Alpha DAC, Weiss DAC202, Chord DAVE, Playback Designs Merlot, T+A DAC8DSD). Which DAC sounds best is in the ear of the beholder and different for everyone. Many people seem to like the dCS sound though.
Disclosure: I have a Rossini and Rossini Clock, so call me biased and arguing for the sake of justifying the high cost.