SoundSmith Sapphire cantilever upgrade to CA Virtuoso?

Buy another (better) cartridge if you want to upgrade, refurbished MM cartridge is nonsence in my opinion. 

For the budget of Clear Audio you could find Grace Level II with original Ruby or even Boron/MicroRidge stylus. 

Did you destroy that unprotected cantilever on Clear Audio? This is a weak part of their design (imo). 

Some cheaper and better cartridges under $700 are always great alternative to refurbishing. Audio-Technica AT-ML170 is one of the best ever. 

Normally people refurbish MC cartridges with SoundSmith, except for a few very popular vintage MM models where the original Ruby cantilever was an option from the manufacturer back in the day. Grace cartridges for example. There was an original Grace RUBY and SoudSmith upgrade is also RUBY (with different stylus tip). This is OK. 

Your Clear Audio has Audio-Technica motor inside, you want to upgrade Aluminum cantilever with Sapphire cantilever. Maybe it will be better, maybe not. Why do you want to keep using Virtuoso (even refurbished) ? Did you try to compare this model to anything else ? 

There are Clear Audio cartridges with Boron cantilever, maybe you can add Boron instead of Sapphire ? 

You'd better ask Peter at SoundSmith what is the optimal. 

Maestro V2 or Zephyr MK III

but why only these two ?