Hey Mike,
I have 4 expansion packs I couldn't get to work with the Sonar Artist, but managed to get them all up and running today. Here's what I did:
My DSF expansion pack sfz files were all installed in a folder called c:\Dimension Pro\ and under that there were folders for each expansion pack.
I determined that Cakewalk Sound Center was installing its own multisamples in this rather long folder name:
c:\Program Files(x86)\Cakewalk\vstplugins\Dimension LE\Modules\Multisamples\Dimension Pro\
I copied everything in c:\Dimension Pro\ (including the subfolders with the wav files) into that folder.
All of the expansion packs then worked. I then deleted the c:\Dimension Pro\ folder and things still worked. Mmm. I'm sure I will never be able to uninstall them without doing it manually. All the sfz files are now mixed in with the Sound Center sfz files.
I had received a reply from DSF on where the samples should have installed and where to move them to but those folders did not exist on my PC. They certainly didn't install where DSF thought they should be.
I don't know if that will work for you. I never had the folder C:\Program Files\Cakewalk\Vstplugins\Cakewalk Sound Center\Modules\Multisamples\ like you did.
Something certainly isn't quite right with the way these install, that's for sure.
Best of luck with it.
Terry