SUT for Lyra Dorian Mono

I can use some advice. Trying my first analog front-end in a long time (30 yrs). Started with VPI Scout with Benz H2 into my tube integrated phono stage. Although I'm still developing my turntable-setup skills, the table/cartridge/amp combination was very musical.

However, wanting to try a mono cartridge, I've installed a Lyra Dorian Mono. (I admire the design of the Lyra mono cartridges.) Since it was low-output, my built-in phono stage needed some help. I added a Quicksilver SUT, but it hasn't worked out well.

There's plenty of gain, even with the low-output Dorian. However, tonality has taken a major hit - higher frequencies are harsh, almost metallic. My tube integrated (Audio Space Reference 300B) is pretty transparent and my speakers too so maybe I'm being overly sensitive but the change with the introduction of the SUT is obvious to all who listen.

Any recommendations on where I might go next? A better SUT? A SUT better matched to my cartridge? Or do I need to look at a high-gain separate phone amp? It seemed a shame to waste the phono in the integrated since it seemed pretty low-noise and neutral but, if that's necessary, I could do something like a Fosgate Signature.

Thanks!