Thanks JohnS for giving me the website of Clavinova 250 and Sbhoa for the wiseful advice..

"I'd be careful if it is getting old. It's possible that a part could go and then you have the expense of sorting it out. Of course, it might give you years of good service. It's not like an acoustic piano where you can look inside to see if it's good for the purpose."
-->thats what im curious, Johns,if one of the tuts out of order, how to repair and tune the piano since the inside cant be seen? Is the expenses higher than those of Acoustic piano?
"I understand that Yamaha keep spares for only three years - which would be tricky if you needed a part replaced."
--->is digital piano have greater chance of not in order than the normal piano? if the Yamaha wont keep the spares, who to help the users?
I feel struggle, as to whether to get the Digital piano for Clavinova 250 or not..

Dont really have the knowlegde of it...
Thanks guys for your replied.
Liz