What would you do?

The most cost-effective way of getting exactly what you want- 3D stage, more liquid natural sound- is Schumann generators. There's a whole bunch of them on eBay and Amazon, they are all dirt cheap, and they all work. Even though they look like a joke, they really work. I started with one thinking it would never work but instead worked so good I now have 7, and another one coming. 

Or if you want to spend money then Synergistic Research makes a couple different versions, pretty much the same thing but of course better and way more expensive. About 10X, 20X. I doubt they are ten times as effective. But they look about a hundred times better, so totally worth it.  (Eyeroll.) 

Seriously, try Schumann generators.  

But even ten of those won't put a dent in your budget. So get Synergistic Research HFT. Get the full speaker kit, and room kits. You will not believe how these things make your speakers disappear! They completely preserve the sound of your system, just make everything incredibly more clear and dimensional. Exactly the sound stage increase you want. 

You will probably still have money left over. Do these things first. Then when you know I know what I am talking about PM and I will hook you up with the really good stuff.

 

Thanks for your feedback,  This is definitely not a direction I was thinking about. I love that! Would appreciate other's thoughts.

Treat the room acoustically.  Look at GIK (though they have a long backlog at the moment) and other companies.  There are plenty of threads on this.  Searching GIK will take you to most of them.