Curious about cartridges.

"Miyajima is not Miyabi :) "

Minor brain cramp while typing

I agree with Mijo; the first thing that crossed my mind when I read your OP is that the Miyajima might sound even better in a higher effective mass tonearm. Fortunately, it’s easy to increase the effective mass of the tonearm, whereas there is very little one can do to do decrease effective mass. You might consider wrapping your triplanar in some dampening tape, for example, which will add some effective mass. Of course, the crude solution is to glue a penny or a nickel to the head shell. I have direct experience with this issue as regards my Koetsu Urushi cartridge, which is also low in compliance. It sounds remarkably better in my FIdelity Research FR64S tonearm than it did in my triplanar. Yet all other things being equal, the triplanar is certainly just as good a tonearm as the FR64S. Because the Koetsu did sound decent in my triplanar, it took years before I even thought of experimenting with higher effective mass.

Miyajima is not Miyabi :) 

Try Miyajima Kansui or Madake, maybe a dealer can help you with upgrade. 

If you like the Miyabi, I think you will also like Ikeda cartridges.

A Koetsu would also match up with your Garrard and Triplaner especially if you have a 12 inch arm

$5-$7K, boy can you do some damage. Lyra Kleos, Ortofon Windfeld Ti, Clear Audio Jubalee Panzerholtz, Van den Hul Crimson Strad and the Grado Lineage Aeon. 

I personally stay away from the cottage cartridge industry. Koetsu and Air Tight should have a heavier arm although you could make them work. The above cartridges are much better trackers. Of all the fine cartridges above the Windfeld Ti holds a special place in my heart. IMHO it is more cartridge for the money than any other cartridge and it's cantilever does not hang out in the breeze for you to snap off.