Just to update the thread.
I have moved to a new room, and the new room has carpet floors and popcorn ceiling. In that room, with the speakers about 12 feet apart, I am getting imaging. If I sit at the sweet spot, I can hear fairly clearly that the voice is coming from the center. However, it seems the soundstage width is limited to the width of the speaker, and I can't really pinpoint the sound location from anywhere else besides the center. For example, in Bon Jovi songs, I hear the voice and the guitar coming from the same "location" in the soundstage. I expect to hear the voice and guitar in different locations.
The room is still not optimal. The right speaker is near a corner, while the left speaker's left side is a large opening which is the entrance to the living room from the other rooms. Also, Audyssey MultiEQ XT seems to mess up imaging, and leaving the receiver on pure direct gives a more pinpoint accurate image.
When I have time, I'll play with placements some more.