Koetsus love a good SUT. They will sound more dynamic and alive into a good SUT than even a good JFET MC stage (like your Chinook) - I own a Sonic Frontiers Line 1 SE+ and Herron VTPH-2A, with which to compare JFET stages to various SUTs on various Koetsu Platinums.
The sound quality differential obviously increases as you improve SUT quality, and decreases as you improve JFET stage quality (to be fair the Herron’s MC stage is excellent) - but I have come to a very strong preference for SUT’s.
The 0.4mV and 5 ohm Koetsu will probably be ideal for a 30x ratio; as low as 15x and up to 40x will also work fine. A Bob’s Devices Sky 30 should be a good match for not too much of money - I’ve used the Sky 40 quite successfully. The older CineMag 1131 is almost as good, if you find a good deal. The Lundahl LL 1931 (16x) is quite good, and well priced (K&K Audio) but I’ve tended to prefer the Sky - it’s close enough that your preference may differ. The Lundahl LL 9206 is decent, and cheap, but the LL 1931 and all Blue-label CineMags are noticeably superior. The best I’ve yet heard is the EAR MC-3 (using its highest, 30x gain setting - now superseded by MC-4 which may not have the same 30x setting?). It handily beats the CineMags and Lundahls on a Koetsu. Really nice device; highly recommended. Combined with the tube MM stage of my VAC Renaissance, it’s heaven on earth. I run an Innovation (now Master Innovation) too. And I’ve got a late-version Koetsu SUT arriving this week; supposedly it should be even better yet. On tonearms - the Fidelity Research FR64 (fx or better yet S) will open up your Koetsu even more.
Use your Chinook at its 45dB gain with the best SUT you can get hold of. I think it will impress you.
Edit: I assumed you were running your Chinook at 60+ dB without a SUT. That's easily the FIRST thing you should change if you haven't already; it will be huge. Even still, I prefer a good SUT with MM gain (40-46 dB) over a full active MC stage, regardless of its gain.
The sound quality differential obviously increases as you improve SUT quality, and decreases as you improve JFET stage quality (to be fair the Herron’s MC stage is excellent) - but I have come to a very strong preference for SUT’s.
The 0.4mV and 5 ohm Koetsu will probably be ideal for a 30x ratio; as low as 15x and up to 40x will also work fine. A Bob’s Devices Sky 30 should be a good match for not too much of money - I’ve used the Sky 40 quite successfully. The older CineMag 1131 is almost as good, if you find a good deal. The Lundahl LL 1931 (16x) is quite good, and well priced (K&K Audio) but I’ve tended to prefer the Sky - it’s close enough that your preference may differ. The Lundahl LL 9206 is decent, and cheap, but the LL 1931 and all Blue-label CineMags are noticeably superior. The best I’ve yet heard is the EAR MC-3 (using its highest, 30x gain setting - now superseded by MC-4 which may not have the same 30x setting?). It handily beats the CineMags and Lundahls on a Koetsu. Really nice device; highly recommended. Combined with the tube MM stage of my VAC Renaissance, it’s heaven on earth. I run an Innovation (now Master Innovation) too. And I’ve got a late-version Koetsu SUT arriving this week; supposedly it should be even better yet. On tonearms - the Fidelity Research FR64 (fx or better yet S) will open up your Koetsu even more.
Use your Chinook at its 45dB gain with the best SUT you can get hold of. I think it will impress you.
Edit: I assumed you were running your Chinook at 60+ dB without a SUT. That's easily the FIRST thing you should change if you haven't already; it will be huge. Even still, I prefer a good SUT with MM gain (40-46 dB) over a full active MC stage, regardless of its gain.