At this time I own a Berkeley Alpha Reference 2 MQA, Tubadour IV, Black Ice Glass FX Tube DAC, and a Marantz KI Ruby SACD player. Prior to that I have owned a PSA PerfectWave MK II, and a Resolution Audio Quantum.
I'm afraid that this won't be a very satisfactory answer but I can't really say that one DAC is clearly superior to another. You would think that the Berkeley Reference 2 ($20,000) would blow away the Black Ice ($800) but I've compared them several times and to my ears the differences are pretty small. I could easily live with the Black Ice and be happy. The Tubadour IV is very similar to the other two but there is something about the sound that I find relaxing.
To help put this in perspective, I can't hear the difference between interconnects either. I've tried numerous times and I even bought a pair of silver cables from Audioquest because so many people said they had a distinctive sound. I compared them using a control (two very similar sounding DACs) and I could not hear any difference at all between the silver cables and Blue Jeans cables.
People who report dramatic differences in DACs must have way better hearing, or have a much more resolving system than I do.