I did notice some weird frequency peaks with the TM's running off the 8 ohm taps of my Rogue CM-II. With some recordings that are very familiar, I was hearing background noise that I know is supposed to be too low in level to be audible. So I question the flatness of the TM's impedance curve.
I ran the Turbo S' for a short time off the 8 ohm taps, and I don't recall hearing anything unusual, though I don't recall if I used some of the same recordings. I was surprised by how neutral they sounded running off the 8 ohm taps.
For my needs, if I were to purchase Spatials again, I don't know that I'd bother with the TM version unless I was running a low power SET amp. And the only difference I could tell between the TM and Tubo S compression drivers is that the TM driver has a diaphragm that's also open to the rear, while the Tubo S' is capped at the rear. So the TM is a true di-pole speaker, and the Turbo-s is only half di-pole, with only the woofers emitting sound to the rear.