I have a HUGE, Guargantuan, massive, behemoth, wooden "entertainment center" between my speakers. It was present one day when I got home from work years ago and to this day I don't remember agreeing to its purchase.... Anyway, "it" was a big reason that my interest in audiophilia waned for several years, thinking that it would be useless to try to get speakers to image the way that I wanted (I heard some old, three box Audio Physic Calderas, and those imaged better than anything I'd heard up to that point). My interest soemhow got piqued by Audiogon listings of some Paradigms (I had Paradigm 9 SE's at the time), and I ended up with Paradigm Studio 100 V3's, purchased at a dealer, who was meticulous in setting them up. They actually managed to image fairly well.
Then I heard the Intuitive Design Summits, had to have them, got them, and the soundstage that they throw is phenomenal, so much so that I posted an Audiogon review about them where I basically went ga-ga over them. (The speakers and the "entertainment center" are pictured in that review.)
So....it's possible to get central imaging even with a huge monstrosity between the speakers. My suspicion is that the imaging would improve still further if the "thing" weren't there between the speakers, however.
-Bill