Bass and echo effects....
From the layout I can see a good and bad...
In most theater scenarios, the room is completely enclosed. Thus sound is reflecting/bouncing around and needs to be controlled within the theater space. Obviously, with the open wall the sound is going to leave the space. However, it COULD
reflect back into the listening space from the living room, creating an echo effect. Not sure how you plan to decorate the living room but some acoustical treatments could help out.
You could even make you own artwork/acoustical treatments. Make a 1-2" deep frame and fill with insulation panels/Rockwool etc. and then cover with a material with a nice pattern on it (maybe something that matches the furniture in the living room...let the wife pick it out!
) and hang them in the living room, foyer, etc. This will help with the echo from the theater AND general echo in the living room.... Just nice, warm acoustics
all the way around. (Hint: my wife responded to that phrase "nice, warm acoustics" when I made wall panels for our front hallway to control the echo)
Sound will leave the room, you just don't want it coming back.... hope it helps!