A:Answer I would try two of them first, you can always add more if it isn't loud enough. I have two paired to act in stereo, and it gets very loud, though my room is less than 1/4 of yours. I still think it would be loud enough with just two -- which of course depends on how loud you like to jam.
You can add as many as you want to your set up, and play the same music and control the volume together. For four speakers, you would create two groups, with a pair of stereo speakers per group. It will work well, they will be synced up - however if your network goes out you will probably need to re-"group" them. This takes about 5 seconds in the application.
