scookall versions of SONAR share utilities and plug-ins

yes, so after installing platinum, (some of) these are updated, and x3 will then use those updated versions
 

TremoJem - I believe there are no upgrades to Melodyne from X3 to Platinum.  As for TH2 - No upgrades here either, BUT there are the addition of "CA Amps" in the Audio FX section (for Pro Channel), which Craig Anderton designed and these additions are Killer Cool if you need good Guitar Amp Sims.