I could be wrong about the default XLN install folder. When I built my PC, one goal was to organize where VST2 and VST3 plugins were located. I gave up on that rather quickly when I got Cubase and reverted back to letting VSTs pick their location.
I think the XLN installer lets you pick the VST folder. I also think the default XLN VST folder is the one it gets from the Windows registry and it is likely the path that Zarg posted...c:\Program Files\Cakewalk\VstPlugins
Regardless, either copy the DLLs as you said or find the folder where they are located and add that to the Plugin Manager search path and you should be good. Don't forget to re-scan VSTs. I don't think the standalone AD programs care about the DLL location since those should only be for plug-ins.