Hi, welcome to Just Answer and thanks for your question!
Kawai pianos are excellent instruments and have had a very good reputation for quality and sound for decades. Kawai's are similar to Yamaha in quality but are usually a little bit cheaper.
In excellent condition, as you describe, this piano should do well on the secondary market and serve a buyer well for years. Considering depreciation over time as well as the used market, I would recommend a selling range today of approximately $5,800-$6,500 in a private sale. Best wishes!
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