Depends on what is important to you. The DGX piano samples have evolved in parallel to those of the P 115/125. While the DGX 630 had a terrible piano sound with one velocity layer, this has much improved since the 650. In view of the price level, it should be obvious that it can‘t offer everything else the SX900 has. If you are mainly interested in piano including weighted keys, it‘s an interesting package, otherwise probably not.