The last top-line board GEM released in the US was the Genesys. The GK-series were kind of low end. What were their previous TOTL and MOTL arrangers?

How do the WK's, SK's, etc. fit into the pecking order? Is a chronology of their product releases posted somewhere?

I've thought about giving them a try, but if there's a problem I am concerned about where I would get service.