Recomendation for speakers BEST for Piano?

I would recommend the ATC line but they cannot be driven with tubes unless you have a mega-watt, 150 watts and above, tube power amp. With appropriate solid state, the ATC's are marvels.

why not?

Sbank is absolutely right. NO speaker has ever matched the Quads in the midrange where most piano and voice (not to mention most music in general) falls. By Medieval music I presume you mean mostly liturgical pieces. The Quads are unparalled with a cappella voice yet equally facile with sackbuts and crumhorns should your Medieval tastes run more secular. The 988 should be sufficient unless you listen to an inordinate number of pianists performing on Bosendorfers which sound better on the 989s. With your musical tastes you must hear these speakers.

Khrys, I beg to differ. Piano resonates throughout it's body with every stroke in subtle low frequencies. When a low note is pounded, the piano cavity is exited all the more. The Apogee can translate these very low frequencies with authority. The Scintilla, Duetta, and Diva all straight line to 20 db. The Scintilla ribbon is every bit as fast as the Quad diaphragm, only the Scintilla can go very loud.

I would contend that a time and phase coherent design is required to reproduce the piano accurately.

In addition, as someone pointed out above, the piano is a percussion instrument and requires not only speed, but great dynamics and FULL range as well. There are tons of overtones and undertones that resonate within the instrument while it's being played.

These requirements leave very few choices. I would agree that the larger (full range) Apogees such as the Divas and Scintillas do a tremendous job at capturing these elements. The other speakers that I recommend are the larger Thiels (3.6 and up).

I really do think that there's also something to the metal drivers. I've NEVER heard a soft-dome tweeter believably reproduce the piano.