If you can't have the speakers further out into the room or closer together, have you tried relocating them to the long wall? I had some older B&W M801s in that kind of arrangement and they imaged amazingly well despite everything being "wrong" about it. The speakers were about 10' apart and 12" out from the wall (to the back of the speaker box). In this position, the speakers became transparent, and it sounded like the music was coming out of the wall between them, with considerable depth in the sound image. I've never heard anything else like that, before or since.
Note: In the setup I just described, the long wall behind the speakers consisted of traditional interior plaster over solid masonry. That combination of materials might have accounted for much of the acoustic success in an otherwise atypical placement. Thus, if you can move your speakers, I'd also recommend that you determine which is the most solid wall in the room, and try the speakers in front of it. Start out with your 10' spread and approximate listening position, and then play with pushing the speakers a few inches toward or away from the wall until the image "focuses" on it. If it isn't working, try putting them a little closer together and repeat the exercise, or adjust the toe-in. Keep an open mind about listening position too, as you change the speaker positions.
Note: In the setup I just described, the long wall behind the speakers consisted of traditional interior plaster over solid masonry. That combination of materials might have accounted for much of the acoustic success in an otherwise atypical placement. Thus, if you can move your speakers, I'd also recommend that you determine which is the most solid wall in the room, and try the speakers in front of it. Start out with your 10' spread and approximate listening position, and then play with pushing the speakers a few inches toward or away from the wall until the image "focuses" on it. If it isn't working, try putting them a little closer together and repeat the exercise, or adjust the toe-in. Keep an open mind about listening position too, as you change the speaker positions.