I am presently operating Sonar X3 Producer and happy with it.
If I would like to upgrade to the NEW SONAR versions, which would be the closest one to producer one to upgrade to?
 
Thank you for any info.
 
Gerry

The version comparison is here:
https://www.cakewalk.com/Products/SONAR/Versions#start
 
Platinum is the new Producer
 
I was really happy with X3(e) Producer and even happier with Platinum.

I was also quite happy with X3 Pro - I only upgraded last Dec because of the lifetime update offer. I'm very happy to have the possibility of the dark UI back that was missing since 8.5 and for that reason alone really I stick with it, but in my experience Platinum crashes a lot more on the same PC that X3 was running fine on and hardly ever crashed (win 7 64).

I jumped on Platinum from X3 about 8 months ago.  Love the new features, fixes and enhancements.  It's the same old X3 with much more added, so it's hard to compare (and catch up).
 
Some features that I find most useful are the upgrades to routing, such as Patch Points and Aux tracks.  My favorite is Synth Recording, where you can record your virtual instrument directly to an audio track now.  But this stuff was added back in the fall of 2015, so it's old news now, LOL! 
 
This is a neat guide to all the things that have been added to Sonar over the last 2+ years since Platinum was released in 2015.  The bakers have been busy!
 
SONAR Update History
https://www.cakewalk.com/Products/SONAR/Whats-New#start

I just got the Sonar Platinum upgrade to X3 producer, the extra drum kits alone for AD2 are more than worth the upgrade cost.

There's something there for everybody!
 
Great bang for the buck

Ive had every version since Sonar 8. Before that I used Pro Audio 9 for many years.
Platinum is the next step up from Sonar X3 (as mentioned by Bob and others).
Its basically the same as X3 with more options, features and less bugs.

There are some versions of Sonar that are ok to stick with and others that you would want to move on from. If you are sticking with an old version of Sonar, it's best if it's one of the following:

7.0.2
8.5.3
X3e