Suggestions on Pre Amp/Amp or Integrated Amp

Simplicity 

Sony  BRAVIA Theater Quad

https://electronics.sony.com/audio/soundbars/all-soundbars/p/hta9m2?srsltid=AfmBOoqUNqs7vsIaRQj9CYWTMUFmnyxT0bF2eg5mokMpI1F8MJPZ3LJm

AI Quickie (just passing it on, I never had an LG)

"While LG manufactures these specific models, AVS Forum discussions indicate that LG TVs often have compatibility issues with external A/V receivers, particularly regarding HDMI ARC/eARC and HDCP handshakes with devices like Blu-ray players.  Consequently, many users pairing LG OLED TVs with third-party receivers (such as Denon or Yamaha) prefer connecting consoles and media players directly to the TV to avoid signal loss or configuration conflicts"

It sounds like surround sound is a requirement given your wife's primary use being movies and that music is not a big priority. 

There isn't much available for affordable high end preamp/surround processors.  By the time you buy a good 5 channel amp, it would be tough for $5k.

I think you'd be best off upgrading to a high end receiver.  There are a ton of options there.  Probably get a nice one for less than $5k. 

That probably isn't much help... 

The Anthem MRX 740 looks interesting.

https://www.crutchfield.com/p_973M7408K/Anthem-MRX-740-8K.html

I have that Anthem integrated.  Works and sounds great!