As for some of the comments with regard to tubes driving Thiel speakers, well I have a pair of Cary Six Pacs Monoblocks rated at 50W in triode mode. I tried them to drive the CS2.4, but they just do no have any dynamic and the music lacked any life and vitality. My conclusion is that the Six Pacs do not have enough power to match well with the CS2.4.
On a larger issue, I am not sure why Thiel in general are a bit difficult to drive. In my experience, time-phase coherent speaker designs tend to be a bit less efficient than other more conventional designs but it shouldn't be difficult to drive. Is it because the Thiel driver themselves have very low impedance?
I myself designed a few time-phase coherent speakers (which I hope to share soon), but the impedance curve or the overall efficiency are not that different if I were the do the same but with using more conventional approach. I supposed it's not because of time-phase coherent but something more intrinsic to Thiel specific driver specs.