I have owned the Townshend Rock Mk3 since 1997. Last year I purchased a Kuzma Stabi S / Stogi S setup. That was really nice too, but the long and short of it is that the Rock is still here and the Kuzma is sold.
Apart from this, I have not compared anything directly to it in my system. Overall, I am very pleased with its performance, so I have no nagging feelings to change it. I have heard so called "superior" TT setups in other systems that don't sound as good as my Rock, but the other gear may also be coming into play.
Instead of changing the table, maybe think about a different arm? I use a Kuzma Stogi Reference and it is spectacular. Many will say that this arm is overkill on the Rock, and maybe it is. All I know is that the performance is excellent. Before the Kuzma, I used an SME V. I prefer the Kuzma. I like it so much that when I do "upgrade" it will be the table and not the arm. With arms of this quality I don't use the Rock's dampening trough, as things sound great without it.
Unfortunately, I can't comment specifically on how these arms improved on the Rega RB300. I switched it out very early on for a Graham and my time with the Rega was just too brief and it was too long ago.
Keep your eyes open for a used Stogi (not reference). The brand has low name recognition here in the states, so they are very reasonable. I see them occasionally pop up in the $500 to $700 range.
I would also consider one of the Origin Live arms.
Changing the arm will cost you a few hundred. You might be surprised by the jump in performance.
