i used to use thiel 3.5's in my main system, & they weren't too bright, even when my adcom gfa-555 was the main amp, & not relegated to subwoofer duty! now, the thiels are doin' yust fine, in the kitchen, powered by a 35wpc audio-innovations integrated, fed from the main system thru its tape outs. hook up a turntable, & then see if the fatigue goes away. or, if ewe have a quality tuner, & uncompressed radio station, is there fatigue here, too? i'd suspect the fatigue is coming from your cd-player. when i had a solid-state preamp, the only way i could get rid of cd-fatigue was by using an ase z-man tubed buffer-stage, even w/speakers other than thiels. now, w/a tubed preamp, i don't need the buffer-stage.
Theil/Classe 6, and listener fatigue
I have Theil 2.2 speakers, a Rotel 855 CD player, a B&K 442 amp, and recently replaced a B&K pro 5 with a classe 6 (a later model than the DR). There is much more detail to be sure but it comes at the expense of fatigue. The highs are either too bright or edgy. Any advice would be greatly appreciated.