Have any of you out there tried the Express Machine Heavyweight Counterweight with your RB300's? I just installed one, so far it is only O.K. I believe there more hype that anything else. The improvements to the sound were a slight increase in treble and bass detail. A slight increase in dynamics. Now on some recordings the improvements were more noticeable than with others, but across the board I would say the improvments were marginal.

My analog system:
Rega P3
Shure V15VxMR
GSP Audio Gram amp 2SE