Don't raise your display to an uncomfortable hight, just to fit a speaker under it. Your eyes should fall 1/3 of the way up the screen measured from the bottom. The tweeters of the left and right speakers should also be on that line (your ears are roughly level with your eyes). Then just place the center as high as you can under the screen.

Pioneer PDP-5020FD, Marantz SR6011
Axiom M5HP, VP160HP, QS8
Sony PS4, surround backs