There are sooooooo many posts about the strengths of these boards. Do a search on each type and see what's been said already. The Yamaha site has audio samples of the 9kpro, and i think the Ketron site does too. Personally, I'd leave GEM out of the mix. Nothing they make can compare to the 9k. I'm not interrested in the SD1 for a lot of reasons, but if you have specific questions about the 9k, VA7, PA80, KN6x - send me an email. I've had them all, and I'll tell why I passed on each one. I'm pretty sure that for the money - the 9kpro is the most complete, professional, expandable keyboard on the market. Even if it didn't have an arranger - it would sell like hotcakes as a gigging keyboard. It's the easiest to navigate by far!