Good thoughts in the preceding posts, except that I would respectfully disagree with this statement:
I don't think that putting mono speakers above and below the TV will make it sound like the sound is coming from the TV. The sound will still come from the speakers above and below the TV. That's what mono is and does. You need stereo, not mono, to do what you want to do.
There is no difference between a pair of stereo signals with identical left and right content (or in this case, top and bottom), and a mono signal fed to two identically placed speakers. You can easily verify that by playing a mono recording through your system; the result will be a focused image centered between the speakers, assuming the speakers and amplifier are connected in phase, and that there are no significant channel imbalances.
Although in BOTH cases I believe that Hhiggins is correct that if the speakers are too close together, comb filtering effects can occur at frequencies which are high enough to make the effects audibly significant.