I tried this a few years ago. I had other good turntables, Tried the Rega after neglecting it for a while, and was not pleased. Experimentally, I bought the cheapest I could find. Although the finish on the shaft was disappointing, the improvement was unmistakeable, and saved the Rega.
I now have a GrooveTracer, which is much better finished.
I think it was my posting of the results which started the flood.
IMHO this the best single upgrade for an old Rega. Any of the subs will be an improvement. Get what you can afford.
Keep them spinning.