What equipment upgrades or tweaks will improve the sound of drums?

How well have you adjusted the crossover, phase/time alignment and levels, between your mains and sub? Are you able to reach realistic levels(ie: have enough dynamic range/power for the room size and liveliness)?

How big is the room?  How big is the sub?  Specific  model would help. 

Enjoyed Rocket Man but I too missed that his classic band got no mention.

Any specific tracks you are looking to deliver the percussion better with?

Udog ...

The lower you get the noise floor, the better the percussion will become.

Better wall outlets. SR Blues perhaps?
SR Blue fuses.
Herbie’s tube dampeners
PPT Total Contact paste.
PPT Omega E Mats
PPT "Stop It" devises.
PPT "The Gate." 

If you do the above, you’ll be able to hear the springs rattling on snare drums and you’ll be able to discern in which direction the brushes are moving on the snares and cymbals. You will be able to hear the difference between vintage drums with animal-skin heads and modern drums with acrylic heads.

If you like rim shots, hard whacks, very defined bass drums, kettle drums, and percussion with dynamics to die for ... take heed in what I’ve posted above. Combined, these items will take your system to levels you have never dreamed possible ... without changing or upgrading any equipment at all.

Frank