Yes,

I'm at the moment having S90 in test.

Have you noticed that piano samples (all of them) get distorted at 1st quarter of keyboard when played tough? Should not be that way when compared to Motif ES 8.

Neither of them are digital piano per se.
They are synthesizers. You may discuss about them in harmony-central.com or motifator.com.

He can discuss them here if he wants. Who made you moderator?

Regarding the distortion, try this:
Listen with effects disabled. Is the distortion still there?
Listen with headphones (more than one pair if possible).
Listen through speakers (more than one pair if possible).
Try to find the source of the distortion.
Of course it's possible that the distortion is in the sample itself, but my gut tells me it's a headphone preamp thing. I've seen this before.

I also experienced distortion when I owned a Trinity. But it was a problem of the line output of the synth, so consider that if you discard headphones as the source of distortion.

A comment to Kenpcola: neither the Motif, nor Tritons, Trinitys, Rolands XPs, or similars are real synths (if you wanna get anal with labels.)