I'm a huge fan of Komplete. I've advised many Sonar users that if they have Sonar and Komplete, they really don't need anything else. A lot of that is because you're getting a ton of content, not just the instruments. They've also made some UI improvements to Kontakt so you can open it without having your brain explode, and deal with macros. Or, you can edit down to the last little parameter.
But to verify Fog's comments - yes, they're all 64-bit and yes, their departure from Kore was sudden, unexpected, and not welcome by Kore users although there was some additional driver development and freebies offered to existing users.
However, the good news is you can get Kore controllers really cheap because people haven't figured out they make nice, general purpose MIDI controllers. I wrote
an article for Sound on Sound on how to use Kore 2 as an ACT controller with Sonar...it does the job very well.