Fastslappy, what I have found over the years, is a little toe-in goes a long way. I have also found that you are better to be at least no more than 12 feet from the speakers, any more than that, you lose the footprint of the sound, especially with a Surround sound setup. Stereo is not so much in that if you have say the speakers twelve feet apart, and your seating is say twenty feet away, your ears will never distinguish the difference between the Left and Right Channels.
Then I have seen setups, that you have the sub right next to the speakers, speakers right next to the tv or cabinet, even though there is enough room with play on either side, and seating at least 8-10 feet away, but the toe in is towards the center of the seating, where no one will even be at majority of the time.
My room setup, I had no choice in how I placed mine, due to I have a in-floor return vent on the right, wall vent on the Left, so the speakers are at those points, with maybe 6 1/2 feet distance between. My wife does still complain to this day, that the RB-81 II's are too large, but for me, they are just right.
You are right on trial and error. I did not run my Audyssey on my Denon AVR-1612, until I got the speakers right, then ran it and listened to them for about two weeks, tweaked them again, ran it again, and then about a month later, ran Audyssey again after watching a lot of action movies. I have not touched them since the last adjustment, and my setup sounds as good as day one. I have of course kept our living room to just an over stuffed chair, a coffee table, a floor rug in front of the couch, then "Black Out" drapes in the room, to help with sound absorption of the highs, but also not to kill the lows, where the room is so dead sounding, that all you are getting are mids.
Now of course the dog does not like it, when the sub kicks on for our Sound bar, when say the tanks are rolling in during Bridge over Remagan, or any of the Transformers movies.