What about some removeable window plugs that can be stored away?
The rears surrounds could be in-ceiling speakers that aim forward. Having them in-ceiling and further back,
would make it easier to set surround levels and keep them out of circulation space. (The rears as drawn,
would be distracting and draw attention to themselves at the nearest seats.)
Tedd, thanks for the link. I haven't looked too much at it yet, but I know you can't generally go wrong following Big. The window plugs could be an idea worth looking into; I haven't even seen someone do something like that before. As for the rears, I hadn't really thought about in-ceilings. I know if I hung bookshelf speakers it probably would be distracting, but what do you mean about it being easier with the in-ceilings to set surround levels?
And there's commercial offerings like the bronze Triads and B&W's
Google Images can be a great research tool too.
As for setting volume levels for surrounds, if you set a level suitable for seating ten feet away, then the volume level will be too loud for a seat a foot or two,
away. That speaker will then draw excessive attention to itself at the nearest seats.
The trick is to get the surrounds up higher and further away, so the differential between seats becomes less.