Indeed the Clavinova Range is very good, but also consider Roland's Range of Digital Pianos. They have features that vary throughout the range that are best for varying needs. The most expensive of the uprights are around £4,000, or approx. $5,800, but they start at around $800, and depending on what you buy, will cater for someone who uses only the piano, with the most realistic action, to someone who requires that along with great technological function.
I went into Beatties yesterday (British Department Store), and played their the Rolands, ond OMG, I recorded myself playin the Maple Leaf Rag, and it knew what key I was in when it showed the score. This may not be a new thing, I dont know, I'm into digitals, but still, it was quite amazing.
So what is it you're after? The most realistic piano (because nothing compares really), or music technology?
--Ash.