Some good advice given above though obviously much of it mutually exclusive! I also have a P2 and have thought about various updates/mods.
The question I have thought about is "what is the goal?" It is possible to basically remake the P2 with an updated platter, subplatter, counterweight, motor, external power supply, arm, etc. At some point, it seems to me to make more sense to save that money toward an RP3 or 6 unless the journey and the incremental process is part of the fun.
In the meantime, a good cartridge is something that can be transferred to a later table so that seems like a great place to go first.
For now I have limited the updates to replacing the original Bias2 cartridge with a Nagaoka MP-110 and using the Baerwald alignment rather than Rega's. Both were improvements. (I also have a Denon DL-110 on a different table. If I had to pick 1, I would go for the Denon.) I haven't heard the other cartridges you or others mention so I can't comment on them.
One thing you don't mention is what you are looking for out of the potential upgrade. Is there something that seems to be missing or is it that vague sense of "I wonder if this could be better?" Thinking about that might help put some of the advice you get, as well as other things you read on-line, in context.
HTH.
Chris