No, I don't think it's a good deal at all.
The reason why you can't find any information about that model is that it's quite old. I'm not sure exactly how old but from the specs it should be at least 7 years old. Floppy disks? I can't even find any computer sold with a floppy disk drive nowadays. Anyway, the one thing I'm sure is that it's older than 3 generations from the current lineup, and since improvements are done each generation (these are electronic products with a high turnover rate) the older models are are worth lesser for the simple reason that the newer ones are better (in functionality, touch, realism, sampling, etc.) I own 2 Casio DPs - one from the previous generation and a current-gen one, and I can tell and feel the difference in both. The newer one is more responsive and has a much better touch.
For $850 you can buy a brand-new, current generation Casio DP. I think you can get the the slim-console type Casio Privia PX-730 for less than that in the US. If you want the bigger Celviano console type, I think the current-gen Celvianos cost more or less $1300. You may even be able to get a big discount on closing-out sales for the previous generation of Celvianos if you look.
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Alfred's AOI Course Bk 2
Frances Clark Contemporary Piano Literature, Bk 1
The Festival Collection Bk 3
30th Week Playing Piano
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+ CASIO PX-720 and PX-730 +
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