I wish to purchase SONAR Artist (new computer) then salvage my old SONAR 6 projects (from obsolete Vista computer) into new "Artist". Would welcome any "words of wisdom", expectations or "cautions".  Thanks LOADS!

If the projects created in SONAR 6 use 32bit DX plug-ins, install 32bit SONAR Artist (assuming the new machine is a 64bit OS). It may also be necessary to install some of the plug-ins which came with SONAR 6. Fortunately both 32bit and 64bit SONAR Artist may be installed on the same machine.

Good thought! Yes my new machine is 64bit and that was one of my concerns. Thanks, scook, for pointing that out. Lastly, I have NOT kept up with upgrades during my 9 years with CW. Is it true Platinum version includes lifetime upgrades?

By default the Command Center installs the version appropriate for the OS. Enable verbose mode in the Command Center settings to see the option to install 32bit SONAR on 64bit Windows. Quite a few of the old 32bit DX plug-ins were not ported to 64bit. This is why you will need to install 32bit Artist. Of course you could install 32bit SONAR 6 too. Chances are it will still work though Win10.
 
Through the end of August, upgrading to Platinum includes updates for life.

Again, thanks for clarification on 32Bit versus 64Bit compatibility issues. Last inquiry scook . . .   my wish is to continue using SONAR 6 (on other computer) BUT disappointed the download is DE-activated in MyAccount, while "Studio Instruments" & "MP3 encoder" are still available. I know SONAR 6 is no longer supported - I'm just irritated CW made it unusable. For industry comparison, Microsoft doesn't support XP, VISTA and prior versions anymore - but they haven't "frozen or taken" them from customers. I "get" this is out of your area . . .  what are my chances of "tech" or sales to "restore" my SONAR 6?

SONAR 6 was never available as a download. All that might be available in your account is the registration information. If that information is not there, you will need to contact CW support to get it added before upgrading. The first full version available for download was X1. The first downloadable upgrade was 8.5 but it depended on an existing installation of SONAR 8. Studio Instruments and the mp3 unlock/encoder products have been downloads for some time.
 
Or is the SONAR 6 Home? I am not very familiar with that product line. If so and the product was originally available as a download, CW support will need to add it back to your account.

No your memory is correct Steve.
 
6, 7, & 8 were never available as a download (DVD only) but from 8.5 onwards this changed but as you rightly said, 8.5 needed to be installed over the top of 8
 
So to the OP, you'd need your original discs to install 6

Such confusion. My regrets scook.  Your suspicion correct.  I have SONAR 6 HOME Studio. It was download only and DOES appear in MyAccount along with serial nbr/registration. BUT, it is DE-activated showing "No downloads are available for this product". So it appears I need to contact CW support to see if they are willing (or authorized) to place it in MyAccount again?

Before you worry about installing the 32 bit version you could do what I've been doing.
I have 100's of old Sonar file starting from 2004. So lots are 32 bit. 
I only have the 64 bit version installed and it's been very straight forward. 
Sonar just warns me as the file opens about missing plug ins. 
They are greyed out when the project opens and still have the original name. 
So I just replace them with the 64 bit versions. 
And a lot of 32 bit plugs ins do load and play using bit bridge. 
So I've never really found a file I can't play even if I made it in Guitar Studio. 
 
One thing I think is important is I have always used CWP files,,, not BUN.