I'm using a Primare A34.2 class d amp which is rated at 150 into 8ohms and "almost double that" into 4ohms - that directly from Primare when I reached out to them inquiring about it.
(Their owner's manual is spartan to say the least.) Virtually every amp I've used in the last few years put out 300 watts into 4 ohm loads.
My listening level is fairly conservative to say the least so I've never stressed the amp nor the Thiels throughout, but I do stress the high current importance in making them perform. The Primare and my BAT pre are breaking in nicely - there is a noticeable difference in sonics after about an hour - for the better. When both are warmed up the same volume setting just blooms - everything simply has more presence and space.
Unsound...I rep some pretty good burgs - where do you reside? I might be able to steer you to some values. But message me aside - this is forum is for Thiel!