Congrats on a fine system ! I had a Cronus Magnum II and it is an awesome sounding amp that creates a large 3D soundstage. Also heard the T66 many times and can imagine a great match with the CM III.
Ordinarily the first thing I would recommend are to seek some KT120 tubes- but in your case the T66 speakers have a powered bass module and the KT120s will offer minimum value.
I do recommend an upgrade to the center preamp tube- try to find a NOS amperex 12AU7 tube- it will upgrade the sound stage and clarity quite a bit- see audiotubes.com (Brent J).
As for the cartridge- a nice low output MC cartridge is a great upgrade from an MM cartridge. You'll hear a cleaner, smoother and more dynamic sound. The Hana is a great value. As for phono stage another great value is the Lehmann Audio Black Cube SE II. It has flexible gain and loading and a two chassis system with isolated large transformer power supply. This makes the sound even cleaner and more dynamic that typical phono stages that use op amps. Those two are no brainers in the audio world and will sound much better than the Ortofon MM. I had an Ortofon 2M black and the upgrade to a low output moving coil was significant. Peace and good luck.
https://www.lehmannaudio.com/phono-stages/black-cube-se-ii-sv-edition.html