Thiel speakers, especially the older models, are the poster children for needing everything right in the chain before them (e.g. electronics, cables) as they tend to be less forgiving than some other brands (e.g. laid back British type speakers). I've owned the 2.3s many moons ago. Do yours have the original tweeters or the later (vented) ones they changed to (and I'm sure someone like Tom or Coherent Source Service would know)? What is the rest of the system like electronics wise, cable wise and what about the room (size, treatments, etc.). My friend also worked at a high end shop years back and I helped deliver many models. The tweeters can sound bright if pushed hard.
I've owned the 2.3s, 7.2s and now the 3.7s. I find the 3.7s to be more forgiving. The 7.2s were better than the 2.3s with regard to brightness as there was a crossover to a midrange at 1kHz before the crossover to the tweeter at 3KHz (and a crossover at 200Hz) vs. the 2.3s at 900Hz and 3kHz.