if you are using Apple's Logic Pro then you might take advantage of the Binaural mixer provided with the app. But anything you do would be only applicable while monitoring/ listening through headphones. As Pethenis (that's greek for dying, right?) said Dolby atmos would be the only medium to provide 3D sound placement with a speaker system.
The ear/brain is not all that good at height differential.
I would try the same sound but pitch them apart -- by how much depends. Then I would hi-pass one and lo-pass the other, but by a significant amount. Meaning, don't hi-pass at 1k and lo-pass at 1k. I would "leave a hole" in between.