Thank you all for your suggestions. Unfortunately for the older tonearm i cannot find the effective mass. I will ask Sumiko who might have this information. I will say that this tonearm design is bad - very easily gets off VTA.
Perhaps I am trying to buy a good cartridge hoping that it can switch over to the new TT, but advice here seems to be to solve for now - in which case maybe i will do nothing at all until i am able to purchase the TT (looking at Origin Live Resolution with Illustrious Arm or Sparta 0.5).
Then again i could buy an AT cartridge for some immediate sonic benefits and trade up when new TT comes along.
Any additional perspectives welcome, and thanks to all who have contributed thus far.