Adimatis at first look the PA500 and the PA800 have a real similar appearance, but once you start looking and playing you'll notice a difference. Key feel on the 500 is not as solid feeling as the 800. Buttons to change styles and voices are not the quality in the PA800. The printing near the buttons that describe what each button does is in larger print. My understanding is no USB for attaching a thumb drive. I believe it takes a flash card instead. Overall, my impression is you're getting a lot of bang for the buck.