@ronkent, I too have been steadily using Thiels for over 30 years. I never considered myself a "headbanger", and as I've said before, ultimate volume levels is a low priority for me. Still, it's a relevant aspect and I'm confident that Jim Thiel gave considered effort addressing it. As one moves up the Thiel range, one of the advantages is that the speakers become more capable of moving more air, with greater dynamic range and ultimate volume levels.
Let's look at what Larry Archibald former editor and former owner of Stereophile had to write about Thiel's and dynamic range.:
https://www.stereophile.com/content/thiel-cs12-loudspeaker-page-2
https://www.stereophile.com/content/thiel-cs2-loudspeaker-larry-archibald-page-2
https://www.stereophile.com/content/thiel-cs35-loudspeaker-page-2
https://www.stereophile.com/content/thiel-cs5-loudspeaker-page-3-0
In some cases more recent models seemed to trade some bass response for greater loudness capabilities.
Thiel's might not have the ultimate volume levels of some of the big horns, but, neither are they limited, like so many panels are. They might not be the best in any single category, but IMHO they can offer very good to excellent performance across the board in every category, save perhaps for generosity in amplifier compatibility.