1 - Horizontal centers were developed primarily for 'ergonomics' and provide good horizontal sound dispersion (but not necessarily good vertical dispersion)
2 - Three identical LCR speakers oriented similarly will make for the best soundstage if you can make the ergonomics work (i.e. good horizontal and vertical dispersion characteristics)
So if I am correct on this I will try to steer my in-laws towards 3 identical LCR's like M60's or 80's. I think we can build that into a false wall with an acoustically transparent screen.
I found these articles very informative and useful in helping make my center (and other) speaker decisions.
Surround-Sound Speaker Placement: Problems and Solutions The Center Channel: Unique and Difficult Music in the Round #4
