I'm running KT-120s, not 150's. The 120s fit inside the stock tube cage, no problem.
I wish folk reporting their sonic observations with these amps would also indicate whether they were running triode, or ultralinear. I run mine in triode, and hear no midrange glare. I find ultralinear to be distinctly inferior to my ears, but it's easy to be fooled by its greater output. When I switch from triode to UL, it sounds louder and clearer, but that is just the increase in volume talking. In reality, it is thinner and less rich in tone.
I wish folk reporting their sonic observations with these amps would also indicate whether they were running triode, or ultralinear. I run mine in triode, and hear no midrange glare. I find ultralinear to be distinctly inferior to my ears, but it's easy to be fooled by its greater output. When I switch from triode to UL, it sounds louder and clearer, but that is just the increase in volume talking. In reality, it is thinner and less rich in tone.