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

Another trick is get yourself a couple of fine 15 inch woofers playing up to 400 Hz. Small speakers and subs nice but they won’t do this. By the way Bruce’s E Street Shuffle is at least to me of reference quality and his artistically peak.

millercarbon >>>

• "Seemed insanely spendy at first. But they sound so good the way I look at it now is I finally have records worthy of the system."

Spot on with the good copies. Tom Port of Better Records gets super-premium prices for his "Hot Stampers." I’ve heard plenty of them before they get to Tom. I have a good friend (Robert) who sells to Tom and he’ll bring them over to my place to play them here first. And sometimes, I end up with Tom’s rejects. Lucky me.

https://www.better-records.com/

Each pressing is so important in getting the best sound, even to the point that I know of collectors (me included) who will have two copies of the same recording because side one, for example, sounds better on one record, and side two will sound better on the other record. And in addition, there are so many recordings that sound better or worse from cut to cut. Same thing for CDs. Yes, we are down-right obsessed.

I wish you were close by. I’d love to dig deep into the vault and pull out some gems for you to hear.

Frank

For me The High Fidelity MC O.5s brought better base. Easy to use and not that expensive in the scheme of things

Don’t know where the OP is, but its safe to bet that, even with a sub, if those small speakers, about the size of kef ls50s, are not in a small room like what they were designed to be in, its a very bad bet that tweaks alone will do much other than put money better spent in the vendor’s pockets.

First thing first. 

No secret here.

It's not clear what your "quality vinyl recordings" are. IMO, reissues are always a disappointment if you have the opportunity to play a period release.

Reissues are fine, but only as a last resort for my ears

Seek out original presses. Your system is fine, LM gear seems to be solid, so you should be using a phono amp on on the same level for maximum vibe.

I never had a problem with drum performance when I had a P5. The plastic  subplatter, when replaced with one of the aftermarket models seemed to add more authority to percussion and bass.