That's a pretty big room for a satellite system in my opinion - I would go with a more traditional speaker setup of a powered subwoofer and 5 or 7 voice matched speakers.
You do not HAVE to have the same brand speaker, but it is ideal to keep the speakers voice-matched, which usually is accomplished by purchasing speakers within the same line from a manufacturer.
For a room that size, I would consider (if your budget allows) looking at Axiom Audio, Aperion Audio, or AV123. All of these companies make a good product at decent prices. Start with a 5.1 system, and build on it. Maybe you can only afford to start out with a sub, center and 4 matched bookshelf speakers. Later when your budget allows, you can add 2 floorstanders from the same line, and move the front bookshelves to your rear center channels, etc.
Hope this helps. I am sure others will jump in with speaker suggestions on this...