Speaker for 11x12 room

 Big glass door may produce a lot of high frequency reflections

The  speakers would be better placed , imo , on the 2.6m wall.    
Diffusion panels on that wall .

That also depends on the kind of piano  : upright piano or grand piano ?

What about a swivel chair .  You could see all around .

11x12 room with an audio system AND a piano? Ah, ok….

The piano is pretty small. It’s upright. idk why I haven’t thought about it I will put it in the bedroom. Unless it will benefit the room acoustics haha. Anyway I don’t want to hug the back wall so it doesn’t really in the way ;)

I would put it on the right wall first.
Here is a list  of 2500-5000 USD speakers so that it may fit your budget used

https://azenfalum.com/diaglist23.htm

+1 on the Joseph Audio. I’d also consider Totem Element Fire V2 or the Fritz Carbon (all used, of course). But that’s for my tastes. What do you want out of a speaker or e correctly, what audible characteristics do you aspire to in your music reproduction system?

And you have a really great amp.   It deserves equally great speakers.