Hello Jim,
I would suggest you visit
www.psrtutorial.com site where you will find lots of styles and voices for almost all makes of keyboards, including Korg, Roland, Ketron, Technics and Yamaha, which are free to download and most have been converted by very professional members of the site and are ready to play on almost any keyboard, including Yamaha.
There is also a wealth of information available on the site too and the people are friendly and extremely helpful if you get into trouble or need advice such as you're after now.
I would also look at Bill Norrie's site. He has all the past Technics styles and voices on there again, completely free to download, plus many that he has composed himself. I know he is a great fan of the Technics KN7000 and I also know some of his styles are better than the originals, particularly when it comes to dannce numbers.
Hope this helps - good luck!
Audrey