Vlad47,
I don't know your amp, and have no idea if KT120s or KT150s will work. I believe that The Tube Store has them in stock, but your should check current stock.
Quicksilver V4 tubes
My monoblocks are from 2006 and I'm looking to retube them I've had the KT 88s in them and now I'm running EL34's but would like to go back to a more powerful tube such as maybe the KT150 would like some suggestions