@pops- I’ve been down this road many times, but my experience is somewhat dated. I started with a Pro-Feel back in 1981 and eventually bought a crazy big CRT "pro" type monitor- a Sony that weighed close to a couple hundred lbs. At that time, there was a limit to screen size, but even before discrete encoded audio for video, I found that having rear channels- using Hafler plus delay, or later Fosgate analog surround processors, made the experience more involving.
I eventually went to CRT projection, very large dropdown screen, Meridian processor, used ARC amps front, back and center (overkill) and a fairly large Snell speaker system with two large Velodyne woofers. This was pre-DVD, and once DVD happened (before that, Laserdisc with AC-3, that big Pioneer player was very nice), I changed processors to a McI, the amps to McI solid state -multi channel basic separates, got a more modern projector, etc.
When I moved in 2017, I pretty much dispensed with the dedicated projection room theatre thing, and got a flat screen and used a smaller surround set up. 5.1. My processor-- a Marantz-- recently crapped out on me, but I found another, later model, factory refurbished. These things appear to be in short supply due to Covid/supply chain, yada. I found some processors back in the old days sounded too digital, but the Marantz, which is not super high end, gives you what you need and then some, and sounds decent. Current TV is a Sony 4k OLED that is a couple years old.
As to waiting until you change TVs, I dunno. I like having the improved sound- as mentioned, I find the whole experience more engaging, even though I’m no longer going "full Cleveland" (if you know what I mean).
I think video has benefitted from trickle down. I remember when the Faroujda line quadrupler was like 20k dollars. Now it is a chip that is included in even cheap Blu-Ray players. I think your biggest hurdle may be lack of supply. I also don’t see the amount of uber high end stuff I did when that market was booming (stereo stores survived on home theatre during the ’90s). I rely more on video streaming than DVD or Blu Ray at this point, so I’m not necessarily getting all that could be had, but it is pretty involving. I did my best to calibrate the TV-- I used to have Joe whatsisname (Kane?) do the calibration service on the projector.
I’m sure others will have more to add, and more current product recommendations. I’m pretty happy with the overall results I get using what I would consider to be less than state of the art in video-- in fact, I think some of this gear is probably better than what was sold 20 years ago, at least from a performance standpoint.