Speaker placement/balance

System is Thiel 3.0a's, Moscode 600, Rogue 66.
I'm trying to get a proper balance from the speakers. It could be that the Thiel's are doing this, but if I move my head a couple of inches one way or the other, the balance on the vocals seems to make a sweeping move in the opposite direction (when I move my head to the left, the balance seems to move towards the right). It also seems that the bass is coming with a bit more volume on the left.
Switching speakers seems to make no difference. I've checked for phase. The room is a bit oddly shaped behind the speakers. The left speaker is several feet out from a typical corner, the right speaker has somewhat more open space behind it; in front of a foyer area.
Any suggestions are welcome.
There's no crying in baseball, and there are no shortcuts in audio. I think you have a good handle on this already. Placement is key and it is trial and error. My speakers are set up asymmetrically, with one speaker about an inch farther into the room, and my chair is also skooshed over a bit to that side, all because of an asymmetrical room that prevents identical distances to the sidewalls. Thiels are also known to have small sweet spots, a fact usually attributed to the steep-slope crossovers used in all their designs. Tweaks to affect this (perhaps only marginally) would include the Argent Room Lens, the ASC Studio Trap and the Totem beak, which was just reviewed on this site.
My initial response is to ask if your speakers are too far apart. What you are experiencing is normal to a degree, but it shouldn't be that dramatic. Try moving them together a few inches and see if that helps. Put marks on the floor for the original placement in case this does not solve the problem.
Have you done your homework in regard to speaker placement? Robert Harley's book is a helpful starting point. Rives can help a lot too!
Just another thought. My experience has been that Thiel's sound better if there placed pointing straight ahead or with very very little toe in if any at all.
You might check your owners manual because i think it also states it there.
Hopes this helps.

Thanks to all for the advice/comments. The problem was really the following: The Rogue 66 pre-amp inverts, so I should have compensated for that by switching the speaker cables at the speaker (red and black to the oppposite). I neglected to pay attetnion to that in the Rogue manual.
Now it sounds proper with lots of information in between the speakers.
Who would have thunk... but I recently upgraded from my solid state integrated amp to tube separates (Rogue Audio separates in fact: an 88 and 66 Magnum) and did NOT change my speaker placement and noticed things to be very different in respect to the horizontal imaging, sweet spot, balance, vertical imaging. I noticed that if I moved my head a foot forward the sound was more focused and the image better defined. I ended up repositioning my speakers due to the new amp & preamp! I ended up using less toe-in and moving the speakers a little further back. WHO WOULD HAVE THUNK?