What digital piano is the best?

I am a musician that plays guitar, drums, and piano. I am looking for a really good sounding digital piano that sounds extreamly close to an acoustic grand. I do not want to spend more than 700 dollars on it. I want it to have a good hammer action, sound, good speakers, both line out and usb outs and I want to be able to use it as a usb controller too. I was looking at the Casio Privia series and I like them a lot. I also know that yamaha is good too. What is the best ?? By the way I don't need a 3000 dollar studio piano.