OK, so I agree that my chair was too far back. I've moved it up closer to my gear, about a foot or so farther than what would make an equilateral triangle. That is where the imaging seems best. But I cannot get over some muffle and also some mid-bass bloat (which I did not have in my previously much larger, more open room, where I sat much further away). It disappears when I stand up, so I tried slowly raising my behind off of my chair and it seemed to disappear with around 4" extra height - the sound gets cleaner and much more open. My ears end up a few inches higher than the center of my speakers' tweeters. So I lowered my speaker stands as low as they can go. I also ordered a set of chair risers (blocks of wood to raise the height of the chair a few inches - these are commonly used by oldsters, making it easier for them to get out of their chair, so an added bonus for me

).
Is it common to end up with your ears higher than the center of your tweeters?
I also turned off my subs to see what would happen. Hmm ... sounds pretty good without the subs. I was surprised. It seems I am hearing much lower frequencies with just the mains in this room compared to my previous room. I'm going to do some measurements with the subs off to see where we're at without them.