I started to teach myself the organ 45 yrs ago. If I had stayed with the same instrument, no doubt I would be a better organist today. On the other hand, I wouldn't have had the inspiration to achieve more, as the arranger keyboards have given me. In the same vein, when I got my first Casio in the eighties, I thought I had arrived. As I got better, I got better toys that could do more. As an example, the KN7000's PM's inspired me to set up much more complex arrangements that can be changed in a hearbeat. The number of voices, all editable, is mind bogling.
Conversely, one can get carried away(myself), for one, and think a new keyboard with snazzy new features will make you even better; wrong. There is a point of diminishing return which makes it more productive to concentrate on your playing, and more fully utilize the tools that you have.
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pa4X 76 ,SX900, Audya 76,Yamaha S970 , vArranger, Hammond SK1, Ketron SD40, Centerpoint Space Station, Bose compact