Why Upgrade the Rega Counterweight?

I recently acquired a new Rega P3-24 with the Elys cartridge. Out of curiosity, I've been looking at the tweaks and upgrades for this unit. Have any of you actually replaced the stock counterweight? What differences did it make?

What about the white Drive belt that's advertised, does this really make a difference? Is the stock belt so poorly engineered that it can be improved with an upgrade? Why wasn't it installed as original equipment by Rega?

I'm really enjoying this table as it is through my Sansui AU20000. I also have the TT PSU which is essential for this table IMHO.

If there were effective tweaks that I could apply to this table to further improve it, I would be interested.
I have an Nad 533 with an RB250 arm. I was very skeptical that changeing the counterweight could make any difference.
Boy was I surprised when I installed a Michell Tecno Weight. The bass was tighter and had more slam. The overall tracking seemed to improve and everything sounded better across the board. It was not a subtle improvement.
Highly recommended. I also installed the white belt but the old belt was so old and stretched that I can't comment on the sonic differences.

I have heard many good things about changing the subplatter
You would also need it to use a heavier cartridge, like the Denon 103 for example.
I changed to the Origin Live endstub/counterweight. Seemed to clarify everything. That said, I would not recommend investing in incremental upgrades to Rega arms. It is money down the drain, at resale time. Better to save up and get a better arm.
The white belt: I bought one and cannot really say it maakes any difference. The white belt was supposed to be a 'limited time offer' so I decided to try one.
I plan on a subplatter someday on my Rega P5. and maybe the type of counterweight that hangs below the arm and rides on two fine 'rails'...
I can say I asked for a different stock subplatter, as when I bought the TT last Spring, I asked to see it in action, annd could see a tiny variation in the glass platter movement, and they let me swap the subplatter with the demo unit. (which was perfectly flat) the movement up and down was only about the thickness of two sheets of paper, but hey, I want it right.
So the stock plastic subplatter can have flaws...
I heard a significant improvement in the bass when I replaced the stock counterweight of an RB300 with a Michell Tecnoweight. Here's a good review that explains the design: Vinyl Engine: Michell TecnoWeight
Thanks to all of you for the great replies. The physics of the Michell design make a lot of sense. You also addressed my primary question of whether you could hear a difference. It's a no brainer, I have a Tecnoweight on order. I especially like the micrometer like adjustment for VTF.

Sometime next year I'll be replacing my Rega Elys. I now see that the Michell design allows for a lot of different cartridge choices that the stock setup limits.

It was reassuring to see that no-one (so far?) furiously defended the white drive belt upgrade. I'd hoped it would only provide a minor contribution to the sound at best, otherwise shame on Rega for initially supplying something so basic (and essential) to their table with an inferior quality. I might consider one when the time comes to replace the original belt but to outright change it as an improvement rubs me the wrong way.

I have other Rega upgrade questions but I'll start a new thread to keep the topics distinct. Sincere thank you's again.