A lot depends on what you are planning.
If you are playing only at home, stereo speakers are fine. If you plan to play in a band or on stage, pro audio speakers and amp(s) are required as you will be playing considerably louder (and likely less concerned about the overall sound, so long as its undistorted, has the bandwidth and is loud enough).
You might consider a tube amp if you plan to use the piano only at home. That could easily take the sharpness out of the high end without loosing any highs (this being that often sharpness is an artifact of distortion of a kind that is common in solid state amps). Tube amps are usually best used with speakers that are fairly easy to drive- 90db+ sensitivity and 8 ohms or more, particularly in the bass region.
If you are playing only at home, stereo speakers are fine. If you plan to play in a band or on stage, pro audio speakers and amp(s) are required as you will be playing considerably louder (and likely less concerned about the overall sound, so long as its undistorted, has the bandwidth and is loud enough).
You might consider a tube amp if you plan to use the piano only at home. That could easily take the sharpness out of the high end without loosing any highs (this being that often sharpness is an artifact of distortion of a kind that is common in solid state amps). Tube amps are usually best used with speakers that are fairly easy to drive- 90db+ sensitivity and 8 ohms or more, particularly in the bass region.