Tonearm/Cartridge compatibility

The two cartridges I’m thinking about purchasing are the Lyra Titan or the Koetsu Onyx. Both carts are 12g in weight and have a compliance of approx. 12cu. I believe this is at 100Hz. My problem is that the effective mass of my tonearm (ZETA) is 16 grams. When you do the math the Resonance calculates to 8.7. Not the most ideal situation, especially when you consider the price of these carts. So my question is: Would I be better off purchasing the above or purchasing a lesser cartridge, in terms of price and performance where the lesser cartridge has a better resonance spec. say around 10.
I think that a resonance at about 8.7Hz is not bad. It is still within the acceptable range. I think that with a high mass arm, you would be better served with the Koetsu Onyx Platinum, which has a compliance of around 9cu, instead of the Lyra with 12cu.

If you want a cartridge with a perfect match for that arm, get a Denon DL103R. It is not as good as the others, but is still very nice, and costs less than $300. A 16 gram arm is spot-on perfect for that cartridge.

If it were my choice, and I had the money, I'd go with the Koetsu. But I think that the Onyx is a little "cold" sounding, and the Rosewood Platinum Signature has better warmth, and is lighter, so that would improve your mass/resonance figure. I vote for the Koetsu Rosewood Platinum Signature.