I disagree that if there are cracks in the soundboard that it would be better to leave it for museum.
See for a better understanding the informations from the steinway website:
Cracks are not that problem because they are in the direction of the strings and not in crossed direction. So even if there are 10, 20 cracks, it will not change the sound, or only almost unaudible.
Much more important is for a grand, that the soundboard does not start to hang down instead having a convex dome. Because the distance strings to soundboard and the tension inside the soundboard is of importance. If there is something wrong here, that has a much more influence on the sound.
My piano has had some cracks too. During restauration, they dried the piano down to 20 percent humidity, so that even some more cracks occured during that. After that they filled the cracks, and put the soundboard back to convex shape. All who heard the piano gave kind comments on the sound, so it worked.
Personally I often prefer the sound of old brand pianos, if they are optimal restaured, over the sound of new ones. Because wood vibrates more freely with time - the resin is crumbled. See violins and guitars - they sound better and better with age, vintage wood instruments are much more expensive than new ones. If the mechanical parts inside a piano are new, same logic applies for pianos too, at least in my opinion.