I would go with a VPI arm, perhaps a used JMW-10 if the new ones are too expensive. For several years, I used the ET-2 (with the high pressure manifold, Wisa pump and storage tank) on a VPI 19-Mk.3. I could never get it to sound like music. Replacing the ET with a JMW-10 was one of the most satisfying moves I've ever made. It has a naturally warm and dynamic sound. I used that combination with a Benz Glider M2 for several years and loved it. Since then I've gone on to several other pivoted arms including the Moerch DP-6 (12" version) and Triplanar VII, which to my ears are even better than the VPI, but I would choose any of the pivoted arms over the ET. To its credit, the ET had the cleanest tracking in inner grooves, but that one area is not worth the sacrifice in overall sound quality. I cannot say how the RB-300 would fare sonically since I haven't heard it in my system.
Dave
Dave