Congratulations on being willing to make this investment for your daughter. First of all let me suggest that you take your time, she who buys in a hurry will probably regret the decision at some point. Read years worth of posts here. This being your first post you have a long road ahead of you.
So you're shopping an acoustic piano. That implies you've made the decision that an acoustic instrument is superior to a digital. For a 6 year old I would say a digital would be fine for the first few years of piano playing. However, an acoustic will take them a bit farther, but will require maintenance (a digital won't). A good digital can be purchased new for much less than you're talking about here.
When purchasing a used acoustic piano plan to have a technician evaluate each instrument you have serious interest in. This will cost between $75 and $150 depending on where you live. Regarding the Kawai you asked about, do you know the model? Do you know if it was manufactured for the USA market (this may be from before Kawai started differentiating between the American market and the rest of the world)? An instrument not manufactured for the American market is what's called a gray market instrument and would be worth less. Does your daughter have a teacher and have you involved that person in this decision (and are you getting useful guidance or are you suspicious of it?)?
These are just some of the issues you should know more about. There's plenty to read about them in other posts so I invite you to use the search feature to find more information.
Edited by Steve Chandler (10/22/12 01:29 PM)
Edit Reason: typo