Look into BACCH4Mac or HAF digital signal processing.
I have no experience with HAF, but am using the BACCH4Mac Intro edition and probably will upgrade to the Audiophile edition (although it is rather expensive.) BACCH is a product of an acoustic research lab at Princeton University.
BACCH minimizes/eliminates crosstalk, manipulates the signal in the time domain, and can create rather dramatic effects on soundstage/imaging. I'm told that effects from the more sophisticated ($) versions, "Audiophile" and up, can be breathtaking. My own experience is that more magic occurs on some recordings than others.
You won't hear much difference on, say, a Diana Krall recording (where all the attention is on one center image). But on one binaural recording, the apparent position of a trombone moved from at/near my left speaker to about 2 meters to the left of the same speaker. Not only the speakers seem to disappear, but the walls of the house can seem to disappear. It can increase the apparent depth and reverb. It does all this allegedly with no impact on the tonality (it is not the same in effect as room correction software or an old school graphic equalizer).
I have highly directive, hybrid electrostatic speakers. These seem to work better with BACCH than some other speakers, so YMMV. There is a 2 week trial of the Intro edition (and it's just software, so if you are not happy with it you don't have to ship anything back).