To be more on topic i heard many high $$$$ DCS set ups ( Kharma room Wilson....etc ) , also MSB and off course many lampi tube dacs , plus countless other DACs
The comment that you have to insert a component into your system for the best evaluation might hold some truth , but its practically impossible without having done a pre selection of some sort .
I think most let reviewers / magazines do some sort of pre selection , whats then left is the elite group.
They test those in their system and buy accordingly .
So the big magazines in the US and europe have a big influence .
I think the big distributors in NL for example follow the absolute sound and add the latest greatest to their portfolio , so they have more or less a safe bet (nobody likes to lose money off course )
The big german magazines like stereo had ( may be still have ) a " Besten liste " with points they gave to components
I just made the WADAX comment because to my ears its in a whole other league, and i dont say that often