Bar none, best DP in this price range.
I have been looking hard for the last year in search of a digital piano for my studio that plays great, has keys that feel good under the fingers, and simply has an amazing piano tone. All the other bells and whistles like zoning, built in synths, etc. were second on my list below the piano sounds. The SP250 is exactly what someone in my position needs. I have gone through countless music stores trying every Yamaha, Casio, Williams, and Kawai I could find, and I kept gravitating toward the Casio PX330 for the longest time. the piano sounds were really good, keys were weighted well, but the on board speakers were worthless and the keys felt VERY plastic-like. The Yamaha P95 was close with almost as good piano sounds, better feeling keys, but much less features and no 1/4" mono outs.
I was walking through a guitar center a few weeks ago and found this one sitting right on the floor on it's included stand and everything. I sat down, and immediately loved what I heard. The speakers are above and beyond any piano under $1,000, the keys feel great with the matte finish on the black keys, and white keys that are smooth but still feel really good. And the weight in the keys is just right. Korg got that right for sure, they aren't light at all but definitely not as heavy as say the PX330.
Most of the sounds are quite good, but the pianos especially are killer, with or without headphones. If you are looking for a practice or studio piano that has great feeling keys that you can pair up with a computer and use software pianos, this is what you need. You won't get a better feeling/playing piano anywhere near this price.