Hi Javier
I am a current owner of the superb Yamaha PSR-SX700 arranger keyboard
I wouldn't worry about this at all. There are, quite literally tens of thousands of styles that will play on the SX700. Many of them available on this site, thanks to the generosity of many members.
In fact I reckon that even if you played 10 styles a day, there would be more than enough to satisfy you for a lifetime.
I have yet to find more than a handful of styles from other keyboards, apart from the Yamaha ones, that will not play, and play well on this keyboard. Most of the Genos and SX900 ones will play, and I also have conversions from Ketron, Roland, Technics and Wersi ones. I have about 200 floppy discs with all sorts of styles, all still work without fuss once transferred to a USB stick.
The Yamaha Club still put out some collections too apparently. Just Google their website.
Plenty to keep you satisfied.
Hope that helps.
Keith.