I was under the impression the Sonitus plugs are VST and not DX, since I can see the dlls in the /Program Files/Cakewalk/Shared Plugins/. But maybe that is the case, and would explain Cubase not seeing them.
I also considered running my SONAR 8.5 install and just installing the desired Plug-Ins - that might work. I also wonder if, in previous SONAR versions, if SONAR was applying a VST wrapper to its DX plugs, allowing other hosts to then use the wrapped DX plugs, and now X1 does not wrap them??
By the way, I wouldn't fault Cakewalk for making their plugs all proprietary now - it is a nice collection included and they certainly have no obligation to other DAW hosts. But I got spoiled using many of these in my other DAWs and editors too