I'd upgrade the table/arm. You are in the vicinity of a Well Tempered Amadeus or Simplex, which would get you an upgraded arm and table. At $2500, you could get both a Simplex and an upgrade at cartridge (20XL if you like the Dyna sound).
Even with the wiring upgrade, I think that the RB300 is probably your weakest link.
Even with the wiring upgrade, I think that the RB300 is probably your weakest link.