Would you be interested in getting a 3rd party Audio Unit plugin ?
I've heard lots of good comments on the Akoustik Piano from Native Instruments. You can read more about this plugin and listen to some previews here :
for what it's worth, I have Akoustik Piano and it's nice. Bit CPU intensive but you can get some very authentic sounds from it.
EastWest also do some good piano plugs/ libraries too so would be worth checking out.
To mix it up further, piano synthesis..... you can get some very good piano emulations out there depending on what kind of flavour you were after.
I've heard there's a new library going to be released by Scarbee and Alicia Keys called "Alicia's Keys".
I'm actually not all that fond of Alicia Keys, but Scarbee make the absolute best Rhodes and Wurlitzer sample libraries on the market bar none, so i have a feeling this will be good.
There was some info on the Scarbee website.