Joe is right,if you can try one. I have an S970 and SX900 and am happy I made the purchase. The PSR is a fine keyboard that I have used for performances for several years. The SX900 sounds more alive with Genos effects,and the speakers are improved. That,coupled with some great new styles and good touch screen made it a no brainer for me. The SX,however, has the new operating system that is an improvement,in most cases,which means a small learning curve. For the most part,however,you will find it very much like the controls of the PSR. You can load all of your PSR 770 registrations if you choose,also.
Bernie