I’ve heard three DACs considered to be superior: the T+A SDV 3100 HV, the Ideon Absolute and the Linn Klimax DSM/3. However, only one of those I heard in my system - the T+A unit. They were all liquid and smooth, but none convinced me (as of yet) to purchase though i now recognize that i was feeding the T+A less optimally. That particular unit (like the one I have - the T+A DAC 200) is much better on native DSD than PCM.
I use a processor to convert everything to DSD 512 in front of the DAC200. It has me wondering about auditioning the SD 3100 again sourced this way.
In any case, the Linn and Ideon DACs were clearly very good, but I heard them in million dollar systems (literally - Wilson Chronosonics and Burmester reference gear for the Linn and MBL Extremes and reference MBL electronics for the Ideon) in huge, well set up rooms. So, while great, what else was I hearing? I came away thinking my system at home is actually pretty good in my limited space. Were the other systems better? Sure, but that much better considering the spend? I don’t have the discretionary income to answer that without bias.
What I expect from a DAC: smoothness, resolution, authentic tonality on piano and voice - the two hardest instruments to get right in my view. The best DACs I’ve heard were just a little bit better than the one I own - I think, but haven’t compared directly. But as has been mentioned elsewhere, you can get pretty great performance if you optimize all elements of your digital system: network, cables, and source. I’ve done so and the performance I’m getting out of my DAC is really close to the best I’ve heard.