Worlds best DAC

Went to CES this year to work on my transition to high Rez digital. I've heard many of the highly regarded players in my room or in others systems in the past. I'm actually very happy with my current cd based sound. As I listened to various DACS playing CD then high Rez, I was not bowled over. High rez was better, but only slightly so. The best (and most different) sound I heard happened to have one similarity. They were 2 non oversampling DACS with tube analog stages(Zanden and Ypsilon). These were without question the most natural sounding digital systems I heard at the show. They made CDsound miles ahead of high Rez. What gives?

PS: I understand the limitations of show auditions.