Every single surround processor (since the introduction of the analog system Dolby Pro Logic) has had the ability to equally distribute the center info equally to the two front L and R speakers and not use any center channel speaker at all. This is sometimes called "phantom center mode". It is WRONG to think of it as a "compromise", it is simply a different alternative and in your case I suspect it would be superior based on your limited placement options and SAF (spousal acceptance factor).
As you know, the only reason there even is a center speaker is because movie theaters have the majority of viewers sitting off axis, however this is not usually true of a home environment with only one or two viewers. The center helps steer one's focus to the center of the screen, especially dialog, even if sitting on an aisle seat. If you don't have people sitting that extreme off axis though, I wouldn't use it at all.
Here's a nifty little experiment you could try. Temporarily disconnect the center speaker, but leave it there, and re-run the Audyssey auto calibration test tone sequence. The system will notice there isn't a center speaker and will automatically engage "center phantom mode" although I'm not sure it actually calls it that. Now, without telling your wife what you have done, ask her to come take a listen and to point with her finger to where she hears the dialog coming from. Turn the TV screen off if you are worried the image will bias her.
If she points to the center of the TV, rather than the speaker which she sits more closely to, then you don't need that center speaker, my man!
[Dealers don't always like to discuss this because it means they might be selling you one less speaker!]
Edited by m. zillch - 6/19/12 at 9:56pm