You are probably midranging yourself to death. B&W, tube equipment, Cardas all have reputations for great midrange, but a bit laid-back sounding. You might need more excitement at the frequency extremes. If your rolling off the ends, you might be turning the volumne up to make up for the lack of excitement, and the loudness might be causing the fatigue. Maybe some of the tubes are weak, which would also contribute to this. This is just a suggestion, as I'm not familiar with all your components.
Why am I experiencing listener's fatigue?
My system is as follows. All thoughts and opinions are welcomed and appreciated.
B&w nautilus 805 speakers with jumpers ,
tweeter/driver grilles removed/tweeters at ear height
Cardas cross single wire speaker cables
Cardas golden reference interconnect
cardas golden power cord
Monster hts 2000 power bar/conditioner
Manley stingray (2 mullard 12at7's and 8 Ei el84's)
sony xa 777es cd/sacd player
7 inch diameter by 18 inches high concrete speaker
stands
blu tac between the speakers and stands
Particle board equipment stand
14 inch (1/4 filled)innertube under the sony
No DIY or professional room treatments at the moment
Stock sony power cord
B&w nautilus 805 speakers with jumpers ,
tweeter/driver grilles removed/tweeters at ear height
Cardas cross single wire speaker cables
Cardas golden reference interconnect
cardas golden power cord
Monster hts 2000 power bar/conditioner
Manley stingray (2 mullard 12at7's and 8 Ei el84's)
sony xa 777es cd/sacd player
7 inch diameter by 18 inches high concrete speaker
stands
blu tac between the speakers and stands
Particle board equipment stand
14 inch (1/4 filled)innertube under the sony
No DIY or professional room treatments at the moment
Stock sony power cord