If 20 bits is all that is possible, why are the engineers chasing the bit rate higher to 64 bit rate now? I suppose there's alot of people who don't understand what they are doing with the bit rate? Maybe this is this akin to selling the $4,000 XLR cable when the $60 cable is as accurate as you'll get. . .
So it's the other features of the unit that make it sound so much better? I suppose it's the transport, the power supply, the more accurate clock, the high slew rate, large current, and digital filters that are playing the larger role of improving the sound quality.
Here is the ad from the Esoteric K-01X features page:
35 bit D/A Processing
The K-01X combines multiple 32-bit DAC chipsets and utilizes 35-bit D/A processing algorithm to convert the PCM signal to analog at a high resolution in excess of 32 bits. 35-bit processing achieves an astounding resolution that is fully 2,048 times that of 24-bit processing. In the digital range, full advantage is taken of high-bit data gradation to minimize calculation errors and provide faithful conversion to analog, thereby attaining outstanding powers of expression with even extremely small music signals.