Transformers have losses, that do not allow them to provide the whole benefit one can expect by perfectly matching the actual source Z to the OSI (Optimum Source Impedance) of the circuit.
The level of quietness of dedicated circuits by THAT or SSM makes it hard to beat.
I have a THAT 151x premp with the OPA1656 on its output which is a DC servo for itself. Works fine, sounds good, very straightforward schematic. The best bang for the buck, really. I use it as a "portable" device.
My primary recording preamps are Soundraft Delta's. Oh, they are tremendous on the drums because they are virtually unity gain at the minimum, so no pads are needed even for close micing with condensers. I sold every other of my studio preamps after I finished the "Delta Project", it just beat the sh*t out of everything, some famous brands included. It needs a lot of work, though. The second op-amp (line in/pre's second stage) oscillates even in the stock version, which is modulated into the audible noise. I was shocked when I found this. As I know it was designed with the 5532 in mind for this position, and it behaves there, I checked, the stock TL072 doesn't.
And I finished a "Cohen" InAmp with the SSM2212 (SOIC replacement for MAT-02) x 2 front-end without caps and servos at all, only phantom blockers. It's close to the Samuel Groner's Monte Generoso design, but there are not so many ways to achieve this goal anyway. It's powered by semidiscrete regs based on Jung's design. Heavy decoupling for every op-amp. One piece of overengineering at my kidney's price. Just sensing the output with maximum gain put a smile on my scope's screen.
So what I hope to achieve with transformers is to outperform that preamp in the "low noise with high gain" game, CMRR and RFI protection included in the equation. But may be I am delusional about their capabilities, I don't know abut the transformers that much.
The LSK170 equivalent is current.
Looks even better, than the original, if I remember its datasheet correctly.