When speaking sounds, it is very subjective. For testing the quality, we need good linear speakers. I am fan of piano acoustic. S90 lacks dynamic at a middle range and decay resonance after key off. RD700SX is fantastic for piano sounding with 4 layers of sample for each key. Effect for Piano has a quite good tuning to simulate the key off resonance.
Ears are very sensitive on dynamic and the quality of sounds is subjective subjet when we talk about the color. We love or we do not love. I have a collection of sounds of piano on my XV88 + SRRX02 and now SXR11! RD700SX may be is my next stage piano.