Looking for a good clean piano soft synth

Have you explored Rapture Session? It comes with Sonar Artist.
 
http://www.cakewalk.com/Products/Rapture-Session
 

XLN Audio Addictive Keys might be worth checking out.
 
Edited to add:
 
Addictive Keys has a demo for Studio Grand that has some limitations but might be useful depending on your needs:
 
From the web site:
NO TIME LIMIT - use it as long as you like
INCLUDES demo version of the acclaimed Studio Grand (4 octaves, 3 mic perspectives)
THE FULL VERSION of Studio Grand offers all 88 keys and 6 mic perspectives - or buy any of the other AK instruments or bundles

True Pianos is pretty decent.  Comes with Plat.  Sample Tank has some good pianos too.

XLN Addictive Keys are sweet indeed, both Grand and Upright.
If you have Focusrite or Novation hardware, you'll get one for free.
Sonivox EightyEight is quite worthwile even at its low price under $20, and has some great layering capabilities.
Moving up in price, yet still under $50, have a look at the ones by Sampletekk, definitely if the 60% off sale is on.
Next, under $100, check out ImpactSoundworks Pearl Grand, SoundIron Emotional Piano and CineSamples Piano-In-Blue.
A little bit more will get you that sweet Mercury Grand by Wavesfactory or the Rosewood Grand by OrangeTreeSamples.
Then also look into the Native Instruments pianos, preferably as part of their Komplete bundle.
VI Labs TrueKeys are wonderful too, but you just missed the $199 sale.
And then there's the Bechstein Digital Grand, but you'll pay $249 for its glory.

Im a huge fan of EZ Keys myself. I know some might say its a cheap sounding synth, but when you Doctor up the sound, its becomes legit. The grand piano is especially a big hit here in the Chuckebaby household.

soens
Here's a back to back comparison of 23 pianos on youtube.
 
The essence of low and high end keys seem pretty easy to capture. I tend to judge more by the midrange keys as they seem like the hardest to capture, by my ears anyway.

 
Nice!
 
I found the MIDI file for the song used in the comparison, Springtime Sundays.  Just google for "SPR_TIME.MID",  or look here:
http://download.midimi.org/midi-100471-download-classical_piano-spr_time.html
 
It's a good way to demo what you have, or any trial versions that you may download
 
And here it is being played on a real piano:
 

The Alien Pianos patches in D-Pro... with that weird yelling part turned off... I love those. 

That Upright is quite nice, there aren't that many well done regular uprights.
For grands, the only VSTs I've actually really liked and didn't feel like I need to wrestle with were Ivory and KeyScape. Different price bracket though. Addictive Keys is decent if you don't need to use the close/wide mics which have crazy high resonance in the highs.

Actually yesterday i purchased the Cakewalk's own Steinway Grand Pianos and they sound amazing

https://shop.cakewalk.com/1244/catalog/product.152055/language.en/currency.USD/?id=YIJkAaHA1f

And the price is more affordable. Love it. Will also try your suggestions


Thanks again, great forum and quick responses

Is this another player/instrument, like Kontakt? Are there a host of 3rd party instruments that can use it, like Kontalt? If not, the PRO $ seems pretty steep, tho you do get 2 lesser $ choices, unlike Kontakt.

I really like their low notes but could never get along with the midrange for more poppy playing, personally. Definitely worth checking out though and an interesting alternative to huge sample libraries.

FWIW -- TruePianos goes for $120 at the moment. I bought mine so long ago that I don't know whether this is the current normal price or a sale.

And, yeah, it's pretty darn good, IMHO.
 

I'm a pianist by profession so by definition pretty nitpicky about the "feel" of any digital piano. Pianoteq sounds quite good and I've used it on demos. The bass notes in particular are amazing, that they did that with pure modeling. Much more "alive" than most sample libraries. I just never really got along with the midrange for anything but ballad style or classical playing. I suppose it must be like Fender purists playing a Blade strat (which I do own and love, haha).