I would search in the fora for commentary on matching cartridge impedance to a SUT. There is a lot to learn in the archives. There have even been a few threads recently.
Fidelity Research made transformers to match their carts. The XG-5 had a "low" position (for carts like the FR-7) with gain of 34dB. The XF-1 L, specifically made for low output impedance carts like the FR-7, has gain of 36dB. They also made an even higher-end transformer by special order called the AGT-5X which would have been customizable for low output impedance carts as well.
Given the Ortofon SPU carts are also similarly low impedance low-output carts (even similar VTF), and I expect the Ortofon SUT was designed with SPU carts in mind, I expect you will do very well with your own step-up.
Fidelity Research made transformers to match their carts. The XG-5 had a "low" position (for carts like the FR-7) with gain of 34dB. The XF-1 L, specifically made for low output impedance carts like the FR-7, has gain of 36dB. They also made an even higher-end transformer by special order called the AGT-5X which would have been customizable for low output impedance carts as well.
Given the Ortofon SPU carts are also similarly low impedance low-output carts (even similar VTF), and I expect the Ortofon SUT was designed with SPU carts in mind, I expect you will do very well with your own step-up.