Contrary to conventional wisdom, most speakers don't disappear. There's always going to be some tell that gives them away. If you close your eyes long enough, can you point at where you think the speakers are and upon opening your eyes, find out you're off a bit?
If so, then I'd turn to treating your room since it's big enough already to accomplish the disappearing trick.
I believe it's due to room interaction as I've only witnessed (no pun intended) the effect in properly set up rooms. Also, you need not spend a small fortune to tame the sound. If you're close enough to someone who you trust, say, an audio salon owner, have him come over and get his/her take on speaker placement.
I say this as I've been over at an owner's home and it seemed to not be the best place to audition (odd shaped room, lots of windows) and yet it was the best 3D presentation I've heard, bar none. When I asked him about it, he said it was by trying different locations until he found the best place.
Easy, peasy.
All the best,
Nonoise