David, it sounds like you've tried this already but it sounds to me like a phase problem. I have an inverting preamp so I swap the leads at the speakers. I have experimented both ways with the speaker cables and on some recordings it makes a huge difference, images way outside and in front of the speaks, and on others it makes no difference. Be careful with the source material you are using, some recordings are not in absolute phase. The phase is often changed many times during recording, mixing, pressing, etc. That's one reason some recordings sound unbelievable in regard to imaging and some sound like crap. That's when most audiophiles like myself get out of the chair and start moving speakers around. Big mistake. Make sure your speakers are connected to your amp in correct phase with each other. Lastly, side wall reflections aren't causing the severe problems you've mentioned although they are the most important to dampen in my opinion. Your image may pull to one side or the other but not like you've mentioned. Hey, you are no doubt in audio hell but rest assured there is a way out. Good luck.
Severe Imaging Problem
Since getting my Aleph-3 I have lateral imaging for the first time.My problem is my room.It is the only practical way I can have speaker set up.The speakers are the same distance from side walls.The left front wall is only 2 feet long then opens to a 5.5 foot wide X 3 foot deep,floor to ceiling window alcove.The right front wall is 6.5 foot long then opens to the alcove.The alcove has windows which are treated with heavy curtains.The alcove also houses myequipment.Obviously I have much more front wall in back of my right speaker.I have side wall treatment as well as front wall.The outside (lateral) imaging is excellent from the right speaker.I couldnt be happier! The left speaker there is little to no lateral imaging.I have reversed I.C.'s