How would you spend my next $5K?

A second sub made a huge difference in my room so that would be my recommendation 

@helomech      +1   The issue with room acoustic treatment is the difficulty/expense and aesthetics that can prove overwhelming to many Audiophiles. Look how many "Agon systems" have that dreaded large flat screen TV prominently showcased. Since the OP never mentioned room treatments or dedicated power lines that would IMO make the most improvement.

Room is the issue for me to add components, but for the money, eh, maybe a bit more, a Naim Uniti with a 20 terabyte drive.  A local dealer that sells it would include his entire library, 16 terabytes of hi def music.  Music of every kind mostly ripped from the thousands of LPs they have and a host of other things that would take too long to describe.

Extra S/812 sub and some bass traps. After that, change out all your Transparent cables. They all add to muddiness of the bass. No bass detail albeit they add some airiness to the upper registers since they pressurize the room with their boominess. I’ve been extremely disappointed with Transparents. Most cables at 1/4-1/6 the price are much better.

I would do number 6 or 7 if u was in your shoes.