RE: Sail quiver: One or more manufacturers?
While most others above have highlighted it, it's worth mentioning again and again. Be sure to acquire compatible masts that will optimize the performance of your sails, whatever brand(s) you decide on.
Personally, I have exclusively sailed Bill Hansen's sails (Windwing and now Hansen Sails) for over 20 years. Needless to say, I'm a proponent of buying a single brand across a sail quiver. There are many advantages to this strategy, but the most important in my mind is better understanding the subtleties of rigging and tuning. With one brand, you have a better opportunity to learn the secrets of unlocking the performance of a sail because you become familiar and comfortable with the sail designer's intent and way of doing things. This doesn't mean that things won't change over time, because they have and will continue to evolve. Yet, I find that the sail designer's underlyiing style tends to be maintained over time. This is difficult to quantify, but I know that others feel similarly when it comes to aligning with specific sail designers and creating a base for customer loyality.
Despite my long term brand loyality, I can readily understand why others might mix and match, or strike a fresh path on occasion, and I wouldn't recommend against it. Many folks differ in how they handle change and adjust to it. Also, there can be quite a bit of merit in aligning with trend leaders for building a varied purpose sail quiver. One might want a certain brand for racing, but something entirely different for wave sailing. Given the completely different attributes and demands associated with these two sailing extremes, it could be very appealing to rely on a theme of diversity.
All in all, there are some great choices out there. It's hard to go wrong these days.