Okay, here we go. You have to get the Origin Live or Expressimo Audio structural mod. It replaces the rear stub, with a better one that is coupled differently. This is the biggest single thing you can do to your arm. Then get the HeavyWeight counterweight from Expressimo. This is not just a heavier one, it has an offset hole, so it drops the weight below the arm tube. Major improvement. The finger lift is microphonic, so you can either grind it off, or damp it well. Set the tracking force to 3 grams, which will defeat the spring, and set the VTF with a scale. It sounds like you may already have done this. You should also get the OL or Expressimo VTA adjuster, so you can really dial-in your VTA. A little self-stick felt on the headshell can help with vibrations before they get to the arm tube. I like the felt better than rubbery compounds like Blu-Tak. The rubbery stuff just catches and releases the vibrations, and the felt quiets them. I have found that 2 rubber O-rings on the Counterweight helped, though. You've already done the re-wiring. Also, play with the tightness of the arm nut that holds it to the plinth. It should not be too tight or too loose, there will be a tightness level that sounds best. Find it by experimentation.
All in all, the RB 300 is a very good arm that can be brought to "giant killer" level with these few mods. The RB250 can go a little higher than the 300, but the 300 will be very close.
If you like the modded RB300, you should hear the OL Silver Tonearm. It will knock you over. You can do better with the OL arms, than any of the up-market Rega arms. For modding, the 250 is best, and the 300 second best. The 600,900,and 1000 are too expensive and don't mod any better than the 300.
If you do all of these mods, your arm will sound about twice as good as it does now. I know that sounds amazing, but it will.
All in all, the RB 300 is a very good arm that can be brought to "giant killer" level with these few mods. The RB250 can go a little higher than the 300, but the 300 will be very close.
If you like the modded RB300, you should hear the OL Silver Tonearm. It will knock you over. You can do better with the OL arms, than any of the up-market Rega arms. For modding, the 250 is best, and the 300 second best. The 600,900,and 1000 are too expensive and don't mod any better than the 300.
If you do all of these mods, your arm will sound about twice as good as it does now. I know that sounds amazing, but it will.