16 bit vs 24 bit vs 35 bit vs 36 bit vs 64 bit DAC sampling


I have limited knowledge about DAC's, but as I understand it, a typical CD player used to have 16 bit sampling, and supposedly no one was supposed to be able to hear the difference between anything more than 16 bit sampling; however, I recently purchased an Esoteric K-01X, which has 35 bit sampling (why 35 bits? no doubt only to differentiate it from their then top of the line 36 bit sampled Grandioso series).  

Now I can hear a big difference between my old Musical Fidelity kW DM25 DAC with 24 bit sampling (circa 2005), and the newer Esoteric DAC with 35 bit sampling, although I'm not supposed to, although maybe there are some other electrical programs playing with the sound besides the sampling rate.  

Now, there are 64 bit sampling DAC's, and I'm wondering how much the ear actually does hear from the sampling, or if it's something else entirely that's making the digital sound better?  

Any insightful opinions or perspectives?  

Thanks.
drbond
Bit depth is the dynamic range possible. 16 bit is 120 db. More bits is unnecessary! 
A DAC can only output whatever the original recording bit rate was. It cannot increase the source's bit rate! You would have to listen at 120 db to hear the noise floor of a 16 bit recording - if you didn't go deaf in 10 minutes!
All these higher bit rates are just oneupmanship to confound the unwary and sell product!
@jasonbourne52

The manufacturers seem to indicate in their literature that the bit sampling is how much the digital steps from the signal are smoothened to sound more analog.  
I believe the higher bit rates make it easier to perform the conversion pushing noise and distortion beyond human hearing, it also improves digital volume control if at least 32 bit is used.