Guitpic1,
I am the owner of 2 Ketron SD7 keyboards. I have owned one of them for 2 years and have used it hundreds of times for senior gigs. I also own a Yamaha Tyros 4 which has sat idle since I got my SD7. However, I do use the Tyros 4 for Special gigs like Christmas because the styles are so good for that time of year.

I have owned and gigged with the following: PSR3000, Tyros 3, Tyros 4, S950, Roland E50 and E80 and the BK-7M module, Korg PA1X , PA2X-Pro, and the PA4X. I can say from personal experience that NONE of the above systems comes close to the realistic sounds and styles of the Ketron SD7. Since I have changed keyboards my number of gigs has doubled! I am playing the exact same songs but just on the SD7 now.

I have zero regrets about buying the SD7 and will continue to use it until the next great thing comes from Ketron.

All this said there is another option. I have been told that currently the very best combination of arrangers is the Tyros 4 or 5 with the Ketron SD40 module. With that setup you can use the Ketron styles and play the Yamaha right hand voices. Or use the Yamaha styles and play the Ketron right hand voices, or just simply drive the SD40 module with the Yamaha keboard.

Hope all this helps.
Deane