I have no problem with my 50 € guitar, but any DP under 1500 € is "no go" for me...

The Casio Digital pianos seem to set the mark for lowest price for a weighted keyboard.

"A weighted keyboard" is like "a guitar". There are several completely different type: light-weighted, normal-weighted, normal-weighted wooden, normal-wighted authentic wooden. Light weight does not mean "bad", the keyboard can be really light then (good for transporting). But the difference when you play it is not subtle. The difference between normal weighted types is not so obvious for novice piano player.

The Kurzweil has the superior sound to everything else.

But not everyone likes Fatar actions.

The thing to keep in mind about a best sounding $3500 digital piano is that the sound still sounds kinky compared to a relatively inexpensive VST like Synthogy Ivory.

For DP (unlike workstations) the price comes mostly from the action. It may be possible to "produce" better sound with Novation + VST, but it is not possible to "play piano" with such combination. And the only reason to have wighted action is to play piano (and only piano).
 
Also sample vs synth sound generation war is not ended yet. Relatively short samples in most expensive DPs is not the result of saving $5 for additional memory.

Funny thing in some circumstances the opposite is true. I have some great sounding VST's and some great sounding hardware.  It takes a load off.  When it comes down to tracking parts, when you do record the PC3K8 it can sound a lot better than a VST, often.  It sits in the mix in a rather effortless and extraordinary way.
 
Piano is not the only thing the Kurzweil can do. It can do tens of thousands of other things and often better than a lot of current VST's. The piano is pretty cool anyway, extremely usable, very convincing especially when the music is good. Listen to the demos. The hardware can just sometimes sound a little fatter and bigger and more convincing than many VST's doing the same sort of job. (bread and butter sounds, eg the Kurzweil doing say a smooth orchestral string legato patch compared to Kontakt doing the same thing)  I like the current sound of the new wave of strange and unusual VST's (like Prism etc, Alchemy) They sit with the Kurzweil doing all the heavy basic stuff very well.
 
Recently on the 96K thread I was talking about an additive VST like Prism sounding so good and it does. But recently I picked up cheap a Kawai K5000 hardware additive synth in mint condition and I cannot believe how huge and fat it sounds compared to my best additive VST. It records so well. I also use a top of the line EMU hardware sampler system and it also sounds incredible. Lastly I use a Roland JD800 and that is fat beyond belief. Most of the time I am carving the excess energy away with the hardware and with the VST's I am often having to fatten them up to keep up with the others.
 
Two actions are better than one. Sometimes the weighted action allows for some more expression. I was amazed and quite surprised how much my other hardware instruments opened up (with many of their sounds) and produced a wider range of everything when controlled by the PC2x keyboard instead of its own.  (Drums!, sorry, weighted not for piano only, everything!) It is the low very soft end of the dynamic range where the weighted excels. I also feel the semi or lighter synth action can also be better too for lots of things. I actually grew up on it and like it best, but I did like having that weighted keyboard around. It was enough to convince me that I will get one permanently one day. Having the octave range is nice too. No transposing.
 

I noticed that you didn't list the Yamaha MOX8 or MOXF8, but I have a MOX8 so I wanted to suggest that you take a look.  The sounds are great and it has a great feature where it handles audio and MIDI through a single USB cable.  So for example my setup is quite simple. . . I have a computer hooked up to my keyboard via USB.  Then my monitors are hooked up to my keyboard.  I can record audio through that cable, control things through the MIDI knobs, and play back audio from the computer through the MOX.  It even has a separate volume control for the audio coming back in from the computer.  Plus it has an additional input for something like a microphone or guitar.  The keys are weighted but they're a little bit lighter than a piano so you can play a little faster.  Overall I think the MOX8 was a great buy.  Now the newest one is the MOXF8 which I think also allows you to load additional samples down the road.  Definitely worth a look.
 
My only criticism of the MOX are that the interface can be a bit confusing.  Simple edits like increasing reverb or EQ'ing are quite easy because there are dedicated knobs for that .You wouldn't want to do in-depth sound tweaking or sequencing on the keyboard in my opinion though without doing a whole lot of studying and practice.   But it comes with editor software for that.  Honestly I don't tweak the sounds all that much. . . if I'm going to get into that I just use a software synth.
 
The suggestions of getting a controller to control a software synth are also good IF you want to only use it at home with your computer.  I kind of like having the additional sounds on the keyboard in case I want to take it somewhere.  That's another bonus of the MOX. . . it's very light.

Some good answers and it does boil down to this: 
 
Are you a piano player or a synth player. 
I find it very hard to use a piano for a synth or organ. 
You can meet the 2 half way with a lot of controllers. 
Do you play live with it or is this just a studio controller 
If it's just for the studio, why waste money on built in sounds?

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My bottom line is to go with the choice that makes sense to YOU.  Anything I offered up was merely additional things to consider when deciding what you want to do.  :)
 
Bob Bone
 

Great answers, and the hardware vs vst argument is a good one.  I will be using vsts also - waiting for Sample Tank 3 before I decide which on a sample library.  The reason that I want hardware is because i I play a  live out of my house each night, (I am primarily a guitar player / singer) playing over tracks / loops I have previously recorded.  I much prefer to be DAW free when I am performing.   When I record backing tracks I will use vsts, but will also use the hardware sounds for certain parts for consistency - I am no trying to record a pristine studio project but rather an emulation of a live performance - it is a interesting difference.  I am leaning towards the Kurzweil PC3 LE.  I like the extra pads, it has the same Fatar keybed as it's big brother.  The Krome is a close 2nd.  I like the sounds a lot, but i already have most of them on the microStation.  I agree about the weighted vs non-weighted Piano / Synth dicussion, but i would like to become a decent piano player, and I also have some smaller controller kicking around.
 
Thanks for the great responses.
 
Grif
 
Playlist of broadcast videos
 
https://www.youtube.com/playlist?list=PL108B16E64EABB509
 
 

CakeAlexS
Addictive keys with a cheap PC setup and a Novation keyboard (or Casio or something) would sound better. Or get a real piano.

Ditto for the Addictive Keys and Novation.  Novation Impulse that is...