I don't want to be rude but that doesn't make much sense...
D->A conversion is a well understood process... It's proven (Nyquist theorem from memory) that sampling at frequency F can pretty much represent the signal exactly at any frequency up to F/2 (minus quantisation from the limited bit depth), but there is absolutely no reason 2 different DACs couldn't generate exactly the same analog output signal from the same digital one within that frequency domain.
Now I understand that impulse response is tricky and that's where the DAC filters come in.
So off hand if you have two 'good' DACs (let's say flat Freq response within the audible domain, noise floor & distortion around -110dB or below), what can possibly make them 'sound different' ? Appart from that filter (and the choices here seem to be the same for all manufacturers, but maybe the DACs you tested have a different default?) or some load related aberration (distortion) in the output analog circuit (but that would have been reflected in the above mentioned noise floor & distortion measurement) ...
I'm really trying to understand here, not lecturing... IE trying to reconcile what I understand of the electronics & math involved (granted quite possibly incomplete) with your experience...
If they sound different to you then there must be *something* that can be measured that differs and I wonder what it can be. There is no magic, it's all pretty grounded in math and physics...