Although the Casio PX830 was a good piano when it first came out, Casio has just released the new Privia PX750 compact digital piano with a much improved key action and acoustic piano sound over the PX830, and it's currently selling for just $799 internet price. Although the speaker system on the PX750 is somewhat less powerful than the PX830, the volume is quite adequate for most homes and the improvements in sound and touch over the older PX830 are amazing, especially for the price. There are some discontinued PX830's on the internet right now for less money and they are good deals compared to what they were, but I would suggest you may be better off getting the brand new PX750. Read my review of this model and you'll learn why: Casio PX750 review
I did like the PX830 however, and the price was reasonable for what it had including the older 1st generation ivory feel piano keys an SD card slot for storage of recorded songs on SD memory cards, a 40 watt audio system with 4 speakers, and fairly realistic piano touch & piano tone and more. Also, the top folded down flat when closing the piano cover, which was kinda cool although I personally like the sliding key cover better because it's more practical in my opinion because you don't have to remove things off the top of the piano when closing the lid on pianos with sliding key covers.
So before you buy a Casio PX830, I would strongly suggest you consider the newer models which will not only sound better but also put you ahead of the technology curve too, and that's almost always a good thing:)