I know absolutelly nothing about the CK Kids as they are just not my type of horse AT ALL and dont bring anything to the table for what we do with our horses.
As far as Poco Bueno, he has brought ALOT to the table as far as " cow ability" and without him, Doc Bar would not have been even a spot on the map. When Doc Bar met Poco Bueno daughters, is when things started happening and history was made. Like stated above, HERDA can be a non issue with sound breeding choices.
As far as Impressive goes, I have seen a number of Impressive descendants who were great athletes in the barrel horse world. I think HYPP is a very sad thing, but those N/N horses HYPP is a non issue.
Testing these horses where applicable is the most important thing.