Suboost, welcome to the forum!
Are Kantas worth slightly over double the price of 936s? Yes, probably - if you are building a system incrementally and it is within your budget. I would say no, if you are not building incrementally.
Do you know what was driving the Focal 936s when you auditioned them? The preamp/amp is an important part of what you will hear (as are interconnects, room treatment, etc.). Your Parasound Halo A23 is a power amp only - not integrated. So there is no preamp built into it. The only preamp component I can tell you have in your system is with the Marantz AV receiver. That receiver is likely very good for movies/shows, etc., but not as good as an integrated amp for 2 channel music listening.
I would sell the Parasound and apply that money towards a good integrated amp with HT (Home Theater) Bypass. That way you can use the front left/right speaker for both home theater audio through the Marantz and 2 channel listening through whatever integrated amp you buy.
The Kantas won’t come close to showing their true potential if you stick with your current components. However, if you are building your systems incrementally, and are interested in the Kantas, I would audition them and see if you feel they are worth the higher price. If so, buy them, but make sure you upgrade your other equipment to a level that matches the Kantas. Hope this makes sense.
Here’s a video about setting up HT bypass: https://www.youtube.com/watch?v=E7f_w1_wy5I