I have owned a pair of Thiel 2.4 for over 15 years now and have had them on multiple amps. Currently they are in a second system my wife uses for TV and background music on some old Rotel mismatched gear.
Power is not the issue but the low impedance is. I think they actually dip down to 2 ohms in the bass. Any amp that doubles down the power at 2 ohm vs 4 is fine. Also the 2.4 have a bit of a rise in the treble on axis so try to use as little toe in as needed to get a good center image. Thiel often recommended no toe in but you need a pretty big room for that as they are a wide dispersion speaker and reflections can be an issue.
Really they are not hard to drive. I had them on a Marantz SR5005 for a few weeks which is a $800 receiver from early 2000s?!? (I needed an HDMI input) and honestly the bass was pretty slamming, Not kidding. It was a big open room to 27’x20’. All the fine details were bad and lost in the receiver though lol
I tried them with a few classD amps which I would not recommend. They were harsh in the highs and had midrange glare. Good bass though.
the best combo I personally used was in my main system on McIntosh MC462 on the 2ohm tap. It really softened up the speaker while still being dynamic. I could listen all day with no fatigue on the Mac.
At their current used prices they are a steel. When I went to replace them I demoed speakers in the $10,000 $15,000 range and had trouble bettering the old Thiels. I think their highs are a bit dated now. They lack air compared to some of the modern designs. Everything else is pretty great though.