Hi Andy.
I don't know that anyone has ever organized an official DAC comparison event, although there have been some individual comparisons along the way. With Danny Richie being a local (luckily for us), many of us have had a chance to hear the DAC-60 he imports compared to other offerings. (It has always done well to my knowledge.)
I think Hoots has performed a few informal comparisons against his P3A, and I know Oscar has had his friend with the Meitner stack involved in a few comparisons as well. As a matter of fact, he was trying to organize another such event
here, although there hasn't been anything posted lately.
The catch is that none of the DACs involved were all compared in the same system, and I don't know that any one person has even been to all of these events. Sorry I can't be of more help!