I'm not sure how tall the K15 is but I think (?) it is comparable in size to my Kawai CX-4, which is the same "continental" style.
I bought it used, to replace a horrible small grand. I was initially thrilled - it sounded so much better.
Now that I've had it a while, I'm a little less pleased. It has a couple of keys that have a sort of harsh sound (been tuned twice) and sometimes it has some annoying rattles that come and go. I'm hoping that it will settle in and some of that stuff will fade.
As to the feel, it is dramatically different from my teacher's Yamaha studio, much softer touch. Not sure if it is better or worse but very different. The plastic key tops are slippery. I'd have never even thought about that before I started playing a lot. It has a practice pedal, which is great. However, it doesn't silence keys in the extreme upper/lower ranges. It has a nice sound, but not nearly as rich in tone as my teacher's studio Yamaha. That also means that in a small room it wouldn't be overwhelming so that might be good.
When I bought it, I didn't feel confident enough playing in public to really give it a good test, or I might have detected these oddities. If you are looking at a used piano, have it checked out by a technician. If you can play, then DO play - not just a song or two but give a thorough playing test if you can, and listen not just to the music but also to whether there are squeaks and rattles.
I think for a brand new pianist, this one I have would be good but if knew then what I know now, I think I'd have waited for a studio size.
My 2 cents.