I think theories are all great to discuss, but in real life, they don't seem to be very dramatic.
I tried the experiment that GranteedEV ask - have my KEF 201/2s angled @ 45 degrees so that they "cross" in front of me.
The only thing I could tell was that the image (vocals) seems to be more dead centered. I do not think it widen the soundstage or anything that dramatic.
I have heard a lot of claims and testimonies about a lot of things in audio, like differences in amps, pre-pros, AVRs, cables, CD/DVD/BD player, DAC, toe-ins, grills off, etc.
In my limited and humble experience, speaker placements can make difference - not always, but they can. And some of the differences they make can be dramatic, but some of them are minute.
For example, moving the Orions far away from the walls seemed dramatic. Moving the Def Tech BP7000 away from walls and aiming their subs away from walls seemed dramatic.
But moving the KEF 201/2, Revel Salon2, and even Infinity P362 around (close to wall, far from wall, angle/toe in, etc.) seemed to make very little difference.
I also remember that my brother's friend Phillip had his Salon2 6 inches from the walls, not toed in at all, and they still sounded superb.
So theories are great and all, but in real life they may not be like you think.
That's how life is, right?
Things never happen exactly the way you plan?