For who ?
It is important to determine which kind of piano will suit your needs.
Your child want to learn the piano. In most cases, one cannot be sure that his interest will become permanent. A beginner's piano may therefore seem an appropriate solution. The smaller uprights of a good make offer every guarantee of quality.
For an adult you may want something more elaborate right from the start in order to maintain the interest of a musically more mature being.
Amateurs should opt for lighter keyboards, to make sure piano technique is acquired in a pleasant way.
For advanced study, a sturdy instrument is essential. Intense piano playing makes great demands on the instruments technical resources (a Bach prelude may require a thousand notes per minute!). The action should be strong and precise. It should run faster than your fingers, not the other way round... A firmer keyboard will help you acquire a good technique.
Concerning the sound, it should be neither too dark nor too clear, to allow you to cover as wide a repertoire as possible.
Finally, trust your ears... and your heart. The ëideal sound' does not exist. Only a sound which particularly appeals to you, a sound with which you will be happy to make music for many years.