Adrian, if material which should be imaged in the center is presently coming from a bit to the right of center, that would indicate that the level calibration needs further adjustment to make the left main louder with respect to the right. If two separated speakers play the same sound at exactly the same level(as heard at the listening position)the sound should appear to come from directly between them for someone sitting directly between them. The image would move to the left or right with the listener if he wasn't directly between them.
