Why Upgrade the Rega Counterweight?

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.

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

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.

You would also need it to use a heavier cartridge, like the Denon 103 for example.

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
also.