buy a Michell Technoarm for $800 or so new here and you get all those features of a modded RB300 but it's way better...
Personally I would try to find a Clearaudio Satisfy arm with the ruby bearings.. mine kills my old RB300 with Technoweight and you can get it with a Rega mount. Sometimes these go up for sale on audiogon for a great deal! This is a very underrated arm in my opinion, as I had intented to buy a Graham Phantom and now I'm quite happy with my Satify arm that upgrade urge is gone... and I'm an upgrade junky....
Personally I would try to find a Clearaudio Satisfy arm with the ruby bearings.. mine kills my old RB300 with Technoweight and you can get it with a Rega mount. Sometimes these go up for sale on audiogon for a great deal! This is a very underrated arm in my opinion, as I had intented to buy a Graham Phantom and now I'm quite happy with my Satify arm that upgrade urge is gone... and I'm an upgrade junky....