The best sounding digital piano is subjective and can vary depending on personal taste. However, there are some digital pianos that are highly praised for their high-quality sounds. These include the Yamaha AvantGrand NW-ADV, the Korg Grandstage 88, and the Roland FP-10. The Yamaha AvantGrand NW-ADV features a Spruce Cone Speaker System, which is designed to replicate the sound of an acoustic piano. The Korg Grandstage 88 has a Stereo Altered Grand, which gives the instrument a warm and full sound. The Roland FP-10 features the SuperNATURAL Piano Modeling Technology, which provides the user with a very realistic and natural piano sound. It is recommended to try out these digital pianos in person to see which one sounds the best to you.