track,
first, welcome to synthzone!
There are many sound modules you can choose from with dozens of piano sounds to control from your keyboard. Yanaha,Roland, Korg Kurzweil on and on, they all make modules. As far as what sounds the best, is something you have to find out for yourself. As you read through the forum you will see that we all have our favorites, because the sound of something is a personal thing. So what I like, you might not.
My suggestion is to try some modules and see what you like.

As far as trading for a new keyboard, that is just about the same answer. What I think would be fair to say is that Yamaha has the most available styles and extra goodies available on the net. Most all the boards though are pretty good and it just becomes a matter of features that one has over the other and what you feel you need to have in a board.
Terry

[This message has been edited by trtjazz (edited 09-28-2002).]