No digital piano's sound like an accoustic one, especially not if you play without headphone.
But to my opinion the yamaha clavinova series is one of the best, i've been using the clp-950 for quite some years now.
And a higher price is definitely not an indication for quality, in case of the clavinova-series it usually just means there are more gadgets and bleeps on it, the mechanics are pretty much the same.
Since taste differs between people, i'd recommend you to go to a pianodealer with alot of digitals and just play them for some time, with and without headphone(!)
gl,
gyzzzmo