Uneven soundstage help, please.


I've got a pair of ATC SCM40 v2's driven by a Musical Fidelity A308 (plenty of power) and overall I'm happy with this combination, given my budget, wife, and listening habits. My system is in an incredibly complex large room, with all sorts of variables in terms of reflection, absorption, etc. And these aren't exactly the same from one speaker to another. I have no choice about speaker placement, given the room configuration.
There's a phenomenon that concerns me, though, that I haven't been able to resolve. In order to get the center centered, I need to position the speakers and listening chair in such a way that the soundstage extends all the way to one speaker, but only three-quarters of the way to the other. It doesn't sound out of whack. It's just a narrower field than I had with my older KEF References, and I wonder if it would sound even better if this was resolved.
Has anyone else faced and solved this? What factors are driving it? I've been living with it comfortably, but I wonder.
Thanks ahead of time for any replies.
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I may be mistaken, but my understanding is if your integrated has a tape in and tape out the equalizer may be (and is ideally) hooked in there.  Someone jump in if that is not correct.

The Schitt Loki at $150 receives glowing accolades on this site.  However, it does not include balance control and that sounds like a feature you would want, assuming your integrated does not have it.  
I just looked at the Schiit a few minutes ago. $150 to run an experiment is doable, but EQ only.
If I recall, I'm using the tape hookup to hear the TV.

To re-state the obvious there are many variables that can affect system channel balance. For years I wouldn't be caught dead owning a component with a channel balance control. Now, with age advancing and a mild hearing loss in one ear the balance control is my friend...