If you really want to optimize for the Denon 103R (a good idea, I think) then I'd recommend that you go for a higher mass tonearm. I've seen a number of people get OK results with medium-mass arms by adding heavier headshells and/or heavier counterweights. But really the 103R sings extremely well with something like a Fidelity Research FR-64s, which is a well-built, high-precision heavyweight arm. Of course if you decide you want higher compliance cartridges, the FR-64s won't be your best companion. But really with the Denon it is a match made in heaven!
HTH
HTH