First things first. No matter how nice the speaker placement in your previous home was, it is entirely irrelevant to what will work in the new place. You need to experiment quite a bit with speaker and listening chair placement. This could be random trial and error or use of some systemmatic methodology (google "Wilson" or "Sumiko" method). If you go with some kind of placement calculation, you will still need to actually do a lot of experimenting.
A room with a nearly square floorplan tends to be problematic, and the high ceiling makes it worse. High ceilings tend to suck the life out of the sound. Still, I have heard very large rooms with high ceilings sound surprisingly good when the speakers were properly placed.
In rooms like this, multiple subwoofers make sense. The use of two or more subwoofers is not to get more bass (most subwoofers can deliver excessive quantities of bass to almost ANY room), but to achieve more uniform bass coverage.
I am less enamoured with the idea of going with bigger speakers for higher sound pressure levels. While I am a fan of big speakers (I like certain horn systems), I particularly enjoy listening at quite low sound levels. Quality, not quantity matters most to me. If you try to overcome the dead sound of your setup with higher volume level, you could make the contribution of destructive room reflections and resonance worse. I would try moving the listening seat closer to the speakers (and move the speakers farther away from the side walls), to make the setup more of a near-field setup; this decreases the contribution of the room to the sound. It is a "free" experiment.
Good luck and I hope everything works out.
