I also suspect the speakers, but I'd try some tube rolling first. Maybe some current stock Gold Lion 6922s. For the 6V6, maybe some Pope NOS or the current stock Tung Sols.
Listening Fatigue & Speakers in Small Room
The main components of my system are B&W N804s, a MF A300cr power amp (225 wpc), a BAT VK-3i, and a MF Nu Vista CD. All cabling is Cardas Golden Reference. I had this set up in my old, 20x24 condo dining room/living room with no problems. Now, I have a house with a dedicated listening room of approximately 10x10x8, and am experiencing listening fatigue. After a little while, the outside of my ears start to hurt. Recently, I have treated the room with GIK bass traps and spot panels which have made the quality of the sound much, much better, but my ears continue to hurt. I'm thinking that maybe the B&Ws are just too big for the room, and that I may need to go to monitors with a sub. Am I on the right track, or could another component may be the culprit? Thanks for your help.