Does an upgrade make sense?

@sfgak Ah the perils of having a good audio system.  How do we do it?

just listening with eyes closed vs. open, light levels, etc., make a huge difference

@sfgak +1. A long time ago I saw a Wilson Audio demo with BAT electronics at a show where David Wilson played a Sting song with full band live in concert, and he turned the lights down and it made a huge difference and was pretty incredible — and I didn’t even like Wilson speakers back then (it was some Watt Puppy version BTW). As soon as I got home I ordered the CD and I still never listen to that song with the lights on ever because it’s just a totally different experience. I find live recordings in general benefit more from low lighting than studio recordings, at least in my experience. BTW, if anyone’s interested in the track I’m talking about it’s “Fragile” from Sting’s Still be Love in the World CD released in 2001. In my system the entire stage and performers like four feet above my speakers and crowd noise like individual whistles and screams come from all around and way outside the speakers, and it really produces the feeling and experience of being in a stadium at a live concert. Really fun. FWIW.

Since you can't move them further away from the front wall  I suggest removing the TV and filling the space with a diffuser.  This will effectively "move the wall back" a bit.

If this isn’t possible you should at least throw a blanket over the TV when listening that’ll also help quite a bit and very simple/easy to do. 

Maybe I could use a little more depth (left right is fine and speakers truly disappear), and maybe a touch more dynamics.

@mahgister @mahler123 These are a couple specific things the OP said he’s looking to improve.

I don’t feel a lack of bass but I understand what they can do to free up my speakers.  But I don’t like crossovers either. 

Understood, but subs will do much more than just add bass, and as I mentioned earlier your entire soundstage will expand in all directions and imaging will also improve significantly obviously as will overall dynamics — all of which you were looking to improve as I recall.  It’s one of those things that once you hear your system with a couple dialed-in subs you won’t wanna listen without them anymore because everything shrinks down and becomes less dynamic.  Last, the SVS subs can be run with speaker-level inputs so no crossover involved if that’s your preference, but you can try it both ways to see which you ultimately prefer.  Anyway, just wanted to fill in a little more info in case it’s helpful. 

Given that you’re mostly happy with the sound now and what you’re looking for, I’d absolutely add a couple subs. Your speakers only go down to 36Hz (-3dB) so you’ll definitely get a better/deeper bass foundation, but you’ll also get an even more expended 3D soundstage and more solid and dynamic imaging within it. The improvements on offer here are not small. I recommend a pair of SVS SB1000 Pro subs because they’re small (about 13” square), will get you down to an honest 20Hz (-3dB), include software so you can dial in the subs from your listening chair with your phone (which is really nice), and a pair only costs as little as $1149 depending on finish. Plus they offer a completely risk-free, 45-day trial (including shipping both ways) so if they don’t work out for some reason just return them, so why not??? You can pay more and get more, but you may well find these are all you need for a significant performance boost on many levels. This one’s a no brainer to me.

https://www.svsound.com/products/sb-1000-pro-subwoofer

Hope this helps, and best of luck.