First of all, please ensure your amp manufacturer is on board. With that disclaimer, I went from a kt120 specified ARC vsi75 to a kt150 specified ARC gsi75 some years ago. I presently utilize an ARC ref75se and love it. The amp specs between the two integrateds are virtually identical but the kt150 is a far superior tube to my ears. It is smoother and yet more dynamic. More texture while having a less grainy presentation. Of course it all depends on the amp and the plate voltage. Your amp may be able to utilize the kt150 but it may not be able to take advantage of its strengths if it simply puts out the same plate voltage into both tubes.
Kt150s cost roughly double so if your amp doesnt exploit its strengths by running them at the appropriate specifications its likely to be an underwhelming result.
Kt150s cost roughly double so if your amp doesnt exploit its strengths by running them at the appropriate specifications its likely to be an underwhelming result.