Hello J20, and welcome to Piano World!
I noticed your thread earlier, but thought I'd wait and let other, more knowledgeable members, respond to your questions about the K18. I did Google the K18 and noticed it was Kawai's 45" studio upright piano. I have not seen or played a K18 in person, but I own an older Kawai K48A (48") upright piano. I really enjoy the K48A, despite it being older. So, I do have some experience with Kawai upright pianos in general.
That said, I would think the K18 is as good as any other higher quality brand. However, only you can decide if the piano suits your taste in sound, tone and key-touch. Also, I would not worry about the fact that the model has been discontinued. Some manufacturers will keep the same model name/designation for years and years, although some changes and modifications in the build may occur. Some companies may change the model name/number/designation to some extent, when design modifications are made.
In my view, the Kawai brand in general is a solid brand, and would be a good choice regardless of the model.
There are members here who may have direct knowledge of the K18, and be able to answer all your specific questions. Maybe my post will get things started for you!