It may be the case that you are expecting too much from your system. Have you heard other systems image as well as you expect from your system?
Most problems can be attributed primarily to the location of speakers. Proper location can be really hard to achieve even by "experts." While there are methods that can be employed for locating speakers (e.g., the Sumiko method, the Wilson method), ultimately, it comes down to moving speakers and listening to the results.
Generally speaking, the further you can get the speakers from the back wall, and to a lesser degree, the side walls, the better the imaging will be. Also, try to avoid big reflective objects between the speakers and in front of the speakers. Bookcases or other uneven surfaces to the side of the speaker is helpful too. If your listening seat is near the wall behind you, that can be a problem too. The best location is with the ears well away from the back wall and the back wall being diffusive (again, a bookcase, or if the wall is bare, a tapestry is great for reducing high frequency glare). If you cannot get five feet or so from the back wall, sometimes it makes sense to get really close to the back wall so the sound is integrated with the back wall reflection; some in between locations, say three feet from a back wall, can be quite bad.
Start with the speakers somewhat close to the wall and then slowly move them forward toward the listening position to find a spot that works. A good location would be one where the imaging is right, and bass response is reasonable. Generally speaking, bass is most prominent with the speaker close to the walls and corners, but, there are all kinds of nodes, so don't assume that after a certain point of pulling the speaker away from the wall, the bass will always be weak. You could find a node where bass is surprisingly strong well away from the walls and corners. The difference between a weak bass point and a strong one can be a matter of less than an inch; placement is that critical (google the Sumiko method of speaker placement).
After finding a reasonable spot, you will still have to adjust for toe-in and for proper tilt of the speaker. Generally speaking, little or no toe-in will give a bigger soundstage and less sound seeming to come directly from the speaker, but, the image may be diffused and location of instruments may not be drawn sharply enough (particularly a central vocalist). More toe-in toward the center listener will sharpen images but cause the size of the soundfield to shrink. Change of the backwards tilt of a speaker will affect tonal quality, integration of the drivers and the apparent height of the image.
One more thing to consider. Good imaging, particularly sound that seems free of the speaker, can only be achieved at one precise spot, usually a central spot equidistant from both speakers. I have hardly ever heard a setup where multiple listeners heard good imaging; move just a little toward one speaker and the image moves into the nearest speaker. The exceptions involved HUGE rooms, with the speakers placed very far apart, and in one case, it also involve three front speakers.
