What we all seem to be dancing around (myself included) is the fact that sound is created by the movement of air. Moving air efficiently requires devices that can displace large volumes of the stuff with relative ease.
Generally speaking, big speakers can do this better than small speakers. Now folks may raise objections to this by citing specific examples where a particularly small, highly efficient, and imminently capable bookshelf speaker can outperform a large, grossly inefficient, and somewhat incapable tower. But that's reaching.
You have a large space to fill with sound
@pberghmans, so the solution should now be reasonably clear from all of our discussions. Your budget is the biggest constraint you face. Personally, I feel it is a bit "light" for what you seek... quality sound, from unobtrusive speakers, to fill a large space at high spl.
Budgets are variable, whereas the properties of sound are not.