Soundstage optimization is not easy. It can be hard identifying the weakest link in the chain that is compromising spacial clues. For most situations, the most likely culprit is the speaker/room interaction. You want to really kill early reflections, that is, those with a delay of less than about 12 millisectonds. If you don't set up and treat your room/speaker/listening position in such a way as to reduce those early reflections to about -20 dB relative to the direct from speaker sound, no other change in equipment is going to fix the problem. Download Room Equalization Wizard (free software) and learn how to use it. The impulse graph will be your main tool on optimizing spacial clues.
REW is a powerful tool that no audiophile should be without. I once was blind, but now I see. REW is that good.