Anyone have one of these products? Which is the best one and how are the acoustic instruments compared to the Yamahas, Rolands, and Korgs?

Welcome to the Arranger Forum!
To find out about Ketron keyboards, use the search function on this forum. You will find intensive discussions on the X1, SD1, plus the new models, and modules.
If you have any specific questions, just ask and you'll get a lot of help.
DonM