Seems like some people like using a "phantom" center channel - that might be a good option, too, considering how high the TV is. The performance might be just as good as an oddly mounted center, and save some money. It would depend upon how many viewing seats you have and how far apart the mains are. You could try that first (only the front L/R, phantom center) and if it didn't perform as hoped, you could add a dedicated center later.
I'm really thinking that some M50's or M60's would be much better in that room if the budget allows.
