Analogue synergy

Although a Koetsu will "work" on a Triplanar and sound good, I get the impression that Koetsu's can sound even better on higher mass tonearms. Koetsu has very low compliance; Triplanar is "medium" mass tonearm. Of course, you can always stick a penny or a wad of gum on the Triplanar headshell to increase its effective mass, instead of finding a whole 'nuther tonearm which might not otherwise be as good as a Triplanar. Seriously, some added mass on the headshell might be a good thing. I think a penny weighs 5 gm. Some prefer blue tac.

If you do get the Brinkmann/Tri/KRS, the weak link will be the Whest PS30R. IMHO you should get the Whest PS30 RDT SE version. It is leaps and bounds above the R in terms of quietness, resolution and dynamics.

Of course if you can get the Whest MC V, it is even much better than the SE. But is twice the price. Worth getting the MC V if your musical taste runs into large orchestrals and big bands where the extra resolution and dynamics over the SE brings you into the venue.

I will try your suggestion of added mass to the Triplanar.
To get the Koetsu RS to work at its best.

As regards to the Whest MC V I've haven't heard this unit yet.So maybe I need to add to my current list of phonostages to demo.
ASR Basis Exclusive
Lamm LP2 Delux.
Audio Research PH7
LFD audio MMC SE

The Triplanar has a multi-weight system for its counter balance, so if you use them right they can be set up to adjust the effective mass of the arm as well.

If you want reduced effective mass, use the weight combination so that the weight(s) are closer to the pivot. If you want greater effective mass, set up the weights so that they are further from the pivot.

I used to own the ASR Basis Exclusive and was contemplating an ARC Ref Phono 2 before buying the Whest MC V.

The ASR and ARC PH7 are not in the same league as the Whest MC V although both are refined and quiet. The MC V is more detailed, dynamic with breathaking leading edges and transients so much so that ASR/ARC sounded slow.