1st I would move piano to bedroom. Then I would start with putting speakers along the 12.1 ft wall. Left speaker spaced 3' from the glass door wall with curtain. The right speaker having about 6ft space between it and left speaker. Position the back of speakers at a distance different than that of the distance from side walls. If possible place a low profile equipment rack along the wall shared with bathroom, not at point of 1st reflection, treat that wall with sound panel at 1st reflection point. Place listening chair about 6ft from front plane of speakers.Treat the wall behind chair with absorption panel. Make adjustments from there.
You have received many good recommendation for speakers. I will only state that I use Fritz carbon 7s in a similar sized room. Sold direct with 60 day trial period. Very tube friendly.