Feribaba,
Using big cinema horns is certainly an option. That's what's used exclusively in evensmall commercial cinemas, because you can get very high SPLs, great dynamics, and you can do it without having to use monster amplifiers. BUT, you have to use careful equalization or the horns will take your ears off. Big EQ'd horn systems can sound really good if the person setting it up knows anything about good sound quality. And that's a big IF.
Most in-wall speakers that are flush to the wall are quite inferior to well designed tower speakers if you're after neutral, uncolored sound. And they are not efficient (sensitive) so you have to use really huge amplifiers.
I don't understand your resistance to using floorstanding main speakers up front.
Regards,
