Hello

I'm searching for a good-sounding piano sound for these synthesizers.
Does anybody has such a sound?

cu,
sekru

Good luck! You are limited by the synths internal waveforms. I also have the X5D and the only decent piano sound you can get out of it is if you are into the classic M1 percussive type piano sound. There are a couple decent sounding COMBI's but if you are looking for realism, look elsewhere.

My Roland XP30 blows the X5D out of the water with the piano sounds from the Session expansion board.