...are so many, it becomes difficult to organize, audition, etc.
..I don't need 200 Ballads, for example...
-I hear you!
When I started with Yamaha (not that long ago really), I was amazed by amount of styles available and I downloaded almost everything there was. And same as you, I soon realized I'm losing overview and that having that many, actually became a burden. When I was searching for a style I needed, going trough so many of them, just took too long: many were actually cr*p, many were duplicates (differed in tempo and/or maybe some voice was substituted), etc. So I decided to sort out only "the best" ones -those which I might need for MY kind of music. To keep story short: at the end, I deleted all of them -except few original styles from SX900 and SX600, that are missing on my SX700.
The only thing that I kept, are Yamaha's expansion packs, because they contain many quite distinct styles and (good!) voices.
Keyboard has 400-500 styles built-in, which is more than enough to find something to start with. And once I find a style that's close enough, I need to customize it anyway (so it will sound to my liking). And, depending on type of some new song I wish to learn, it happens quite often, that I decide to make style from scratch.
Sorry for not giving you direct answer.. hopefully I gave you something to think about.
Bogdan