(i.e not all DAC will sound the same since I think that 20-30 dB differences should be easily audible to the ear no?)
If the SNR was 20 or 30 dB you'd be able to hear that, but the difference between 98 and 128 is meaningless. Because you can't hear noise that is 98 dB below the signal in the first place. In a very, very quiet room, you may be able to hear noise that is 84 dB (14 bit) below the signal.
Pioneer VSX-1018AH-K, PDP-5020FD, DV-79AVi
Axiom M22s, VP150, QS8s
Sony PS3, surround backs