Could be very interesting for me. I have an Octave V110 designed for the KT120 and I don't care for the KT120 sound (but like a little more 'control' because of a little more power). I also have the option (though a switch on the back) to go to the EL34/6550/KT88 tubes (my Ei KT90's sound great at the higher plate voltage - KT120 setting). The KT150 may be more to my liking if they are warmer and more natural sounding. To me the KT120 is forward and bright.
That's my opinion
That's my opinion